#include <bits/stdc++.h>   using namespace std;   long long int func(long long int n) {     long long int res = 0;     while (n != 0) {       n /= 10;       res++;     }     return res;   }   int main() {     long long int w, m, k;     cin >> w >> m >> k;     long long int n = func(m), tr = w / k, res = 0;     while (tr > 0) {       long long int dum = pow(10, n) - m;       res += fmin(tr / n, dum);       tr -= dum * n;       m += dum;       n++;     }     cout << res;   }   