#include <iostream>
#include <vector>
#include <cmath>

using namespace std;

int main(void){
    double a, b, c;
    cin >> a >> b >> c;
    long long ans = round( (c*((b-c)/(a-b))+b) -(a*c-((b-c)/(a-b))*b));
    cout << ans << endl;
}