//#include<bits/stdc++.h>

#include<stdio.h>

#include<math.h>

#include<algorithm>

#include<string.h>

using namespace std;

#define N 200005

#define LL long long

int wa[N],wb[N],wm[N],wv[N],sa[N];

int *rank,height[N],s[N],a[N];

//sa:字典序中排第i位的起始位置在str中第sa[i]

//rank:就是str第i个位置的后缀是在字典序排第几

//height：字典序排i和i-1的后缀的最长公共前缀

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

{

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

}

void getsa(int *r,int *sa,int n,int m)

{

    int *x=wa,*y=wb,*t;

    for(int i=; i<m; ++i)wm[i]=;

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

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

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

    for(int i=,j=,p=; p<n; j=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<m; ++i)wm[i]=;

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

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

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

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

        {

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

        }

    }

    rank=x;

}

void getheight(int *r,int *sa,int n)

{

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

    {

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

    }

}

int k;

char s1[N];

int len1;

LL solve(int n,int len,int k)

{

    int *mark=wa,*sta=wb,top=,i;

    LL sum=,num[]= {};

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

    {

        if(height[i]<k)

        {

            top = num[] = num[] =;

        }

        else

        {

            for(int size = top; size&&sta[size]>height[i]-k+; size--)

            {

                num[mark[size]] += height[i]-k+-sta[size];

                sta[size] = height[i]-k+;

            }

            sta[++top] = height[i]-k+;

            if(sa[i-]<len) mark[top] = ;

            if(sa[i-]>len) mark[top] = ;

            num[mark[top]]+=height[i]-k+;

            if(sa[i]<len) sum+=num[];

            if(sa[i]>len) sum+=num[];

        }

    }

    return sum;

}

int main()

{

    int i,j;

    while(~scanf("%d",&k),k)

    {

        scanf("%s",s1);

        int n = ;

        for(n = ;s1[n]!='\0';n++)

            s[n] = s1[n];

        s[len1=n] = '#';

        scanf("%s",s1+n+);

        n++;

        for(;s1[n]!='\0';n++)

            s[n] = s1[n];

        s[n] = ;

        getsa(s,sa,n+,);

        getheight(s,sa,n);

        printf("%lld\n",solve(n,len1,k));

    }

    return ;

}