#include <iostream>
#include <vector>
#include <utility>
#include <algorithm>
#include <string>
#include <stack>
using ll = long long;
#define MOD 1000000007
using namespace std;

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