#include <iostream>
#include <vector>
#include <string>
#include <cstring>
#include <math.h>
#include <cmath>
#include <limits.h>
#include <map>
#include <set>
#include <queue>
#include <algorithm>
#include <functional>
#include <stdio.h>
using namespace std;

long long MOD = 1000000007;

int main() {
    double a,b,c;
    cin >> a >> b >> c;
    double r = (c-b)/(b-a);
    double d = b-a*r;
    cout << static_cast<int>(c*r+d) << endl;
    return 0;
}