#include <iostream>
#include <cstdio>
using namespace std;
#define rep2(x,from,to) for(int x = (from); x < (to); ++(x))
#define rep(x,to) rep2(x,0,to)

int main() {
	int a, b, n;
	while(scanf("%d %d %d", &a, &b, &n) != EOF) {
		int r = 0;
		a = a % b;
		a *= 10;
		rep(i,n) {
			rep(j,11) {
				if(b * j > a) {
					r += j - 1;
					a -= b * (j - 1);
					break;
				}
			}
			a *= 10;
		}
		cout << r << endl;
	}
	return 0;
}