/* 3415 */

 #include <iostream>

 #include <sstream>

 #include <string>

 #include <map>

 #include <queue>

 #include <set>

 #include <stack>

 #include <vector>

 #include <deque>

 #include <algorithm>

 #include <cstdio>

 #include <cmath>

 #include <ctime>

 #include <cstring>

 #include <climits>

 #include <cctype>

 #include <cassert>

 #include <functional>

 #include <iterator>

 #include <iomanip>

 using namespace std;

 //#pragma comment(linker,"/STACK:102400000,1024000")

 #define sti                set<int>

 #define stpii            set<pair<int, int> >

 #define mpii            map<int,int>

 #define vi                vector<int>

 #define pii                pair<int,int>

 #define vpii            vector<pair<int,int> >

 #define rep(i, a, n)     for (int i=a;i<n;++i)

 #define per(i, a, n)     for (int i=n-1;i>=a;--i)

 #define clr                clear

 #define pb                 push_back

 #define mp                 make_pair

 #define fir                first

 #define sec                second

 #define all(x)             (x).begin(),(x).end()

 #define SZ(x)             ((int)(x).size())

 #define lson            l, mid, rt<<1

 #define rson            mid+1, r, rt<<1|1

 const int maxl = 1e5+;

 const int maxn = maxl * ;

 char as[maxl], bs[maxl];

 int a[maxn];

 int rank[maxn], height[maxn], sa[maxn];

 int wa[maxn], wb[maxn], wc[maxn], wv[maxn];

 int S[maxn][];

 int K;

 bool cmp(int *r, int a, int b, int l) {

     return r[a]==r[b] && r[a+l]==r[b+l];

 }

 void da(int *r, int *sa, int n, int m) {

     int i, j, *x=wa, *y=wb, *t, p;

     for (i=; i<m; ++i) wc[i] = ;

     for (i=; i<n; ++i) wc[x[i]=r[i]]++;

     for (i=; i<m; ++i) wc[i] += wc[i-];

     for (i=n-; i>=; --i) sa[--wc[x[i]]] = i;

     for (j=,p=; p<n; j*=, m=p) {

         for (p=,i=n-j; i<n; ++i) y[p++] = i;

         for (i=; i<n; ++i) if (sa[i] >= j) y[p++] = sa[i] - j;

         for (i=; i<n; ++i) wv[i] = x[y[i]];

         for (i=; i<m; ++i) wc[i] = ;

         for (i=; i<n; ++i) wc[wv[i]]++;

         for (i=; i<m; ++i) wc[i] += wc[i-];

         for (i=n-; i>=; --i) sa[--wc[wv[i]]] = y[i];

         for (t=x,x=y,y=t, x[sa[]]=, p=, i=; i<n; ++i)

             x[sa[i]] = cmp(y, sa[i-], sa[i], j) ? p-:p++;

     }

 }

 void calheight(int *r, int *sa, int n) {

     int i, j, k = ;

     for (i=; i<=n; ++i) rank[sa[i]] = i;

     for (i=; i<n; height[rank[i++]]=k)

     for (k?k--:, j=sa[rank[i]-]; r[i+k]==r[j+k]; ++k);

 }

 void printSa(int n) {

     for (int i=; i<=n; ++i)

         printf("%d ", sa[i]);

     putchar('\n');

 }

 void printHeight(int n) {

     for (int i=; i<=n; ++i)

         printf("%d ", height[i]);

     putchar('\n');

 }

 void solve() {

     int n = , nn;

     for (int i=; ; ++i) {

         if (as[i] == '\0') {

             nn = i;

             break;

         }

         a[n++] = as[i];

     }

     a[n++] = ;

     for (int i=; ; ++i) {

         if (bs[i] == '\0') {

             break;

         }

         a[n++] = bs[i];

     }

     a[n] = ;

     da(a, sa, n+, );

     calheight(a, sa, n);

     int top;

     __int64 tot, ans = ;

     // handle as with bs

     top = ;

     tot = ;

     rep(i, , n+) {

         if (height[i] < K) {

             top = ;

             tot = ;

         } else {

             int cnt = ;

             if (sa[i-] < nn) {

                 ++cnt;

                 tot += height[i] - K + ;

             }

             while (top && height[i]<=S[top-][]) {

                 --top;

                 tot -= 1LL * S[top][] * (S[top][] - height[i]);

                 cnt += S[top][];

             }

             S[top][] = height[i];

             S[top][] = cnt;

             ++top;

             if (sa[i] > nn)

                 ans += tot;

         }

     }

     tot = ;

     top = ;

     rep(i, , n+) {

         if (height[i] < K) {

             tot = ;

             top = ;

         } else {

             int cnt = ;

             if (sa[i-] > nn) {

                 ++cnt;

                 tot += height[i] - K + ;

             }

             while (top && height[i]<=S[top-][]) {

                 --top;

                 tot -= 1LL * S[top][] * (S[top][] - height[i]);

                 cnt += S[top][];

             }

             S[top][] = height[i];

             S[top][] = cnt;

             ++top;

             if (sa[i] < nn)

                 ans += tot;

         }

     }

     printf("%I64d\n", ans);

 }

 int main() {

     ios::sync_with_stdio(false);

     #ifndef ONLINE_JUDGE

         freopen("data.in", "r", stdin);

         freopen("data.out", "w", stdout);

     #endif

     while (scanf("%d", &K)!=EOF && K) {

         scanf("%s%s", as, bs);

         solve();

     }

     #ifndef ONLINE_JUDGE

         printf("time = %d.\n", (int)clock());

     #endif

     return ;

 }

 from random import randint, shuffle

 import shutil

 import string

 def GenDataIn():

     with open("data.in", "w") as fout:

         t = 20

         bound = 10**2

         lc = list(string.lowercase)

         for tt in xrange(t):

             k = randint(1, 10)

             fout.write("%d\n" % (k))

             length = randint(100, 500)

             line = ""

             for i in xrange(length):

                 idx = randint(0, 25)

                 line += lc[idx]

             fout.write("%s\n" % line)

             length = randint(100, 500)

             line = ""

             for i in xrange(length):

                 idx = randint(0, 25)

                 line += lc[idx]

             fout.write("%s\n" % line)

         fout.write("0\n")

 def MovDataIn():

     desFileName = "F:\eclipse_prj\workspace\hdoj\data.in"

     shutil.copyfile("data.in", desFileName)

 if __name__ == "__main__":

     GenDataIn()

     MovDataIn()