#include <cstdio>

 #include <cstring>

 #include <algorithm>

 #define LL __int64

 using namespace std;

 LL w,m,k;

 bool ok(LL c)

 {

     LL ans=;

     LL x2=m+c-;

     int t1=;

     LL b=x2;

     while(b)

     {

         b/=;

         t1++;

     }

     int t2=;

     LL b1=m;

     while(b1)

     {

         b1/=;

         t2++;

     }

     if(t1==t2)

     {

         ans+=c*t1*k;

         if(ans<=w&&ans>=) return true;

         else return false;

     }

     LL x1=;

     int a1=t1-;

     while(a1--)

     {

         x1*=;

     }

     ans+=(x2-x1+)*t1*k;

     LL x3=;

     int a2=t2;

     while(a2--)

     {

         x3*=;

     }

     ans+=(x3-m)*t2*k;

     for(LL i=x3; i<x1; i*=)

     {

         t2++;

         ans+=(i*-i)*t2*k;

     }

     if(ans<=w&&ans>=) return true;

     else return false;

 }

 int main()

 {

     while(scanf("%I64d%I64d%I64d",&w,&m,&k)!=EOF)

     {

         LL l=,r=w;

         LL ans=;

         while(l<=r)

         {

             LL mid=(l+r)/;

             if(ok(mid))

             {

                 ans=mid;

                 l=mid+;

             }

             else

                 r=mid-;

         }

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

     }

     return ;

 }