#define _USE_MATH_DEFINES
#include <cstdio>
#include <iostream>
#include <sstream>
#include <fstream>
#include <iomanip>
#include <algorithm>
#include <cmath>
#include <complex>
#include <string>
#include <vector>
#include <list>
#include <queue>
#include <stack>
#include <set>
#include <map>
#include <bitset>
#include <numeric>
#include <limits>
#include <climits>
#include <cfloat>
#include <functional>
#include <iterator>
using namespace std;

int main()
{
    int x, y, z;
    cin >> x >> y >> z;

    double r = (z - y) / (double)(y - x);
    double d = z - y * r;

    double tmp = z * r + d;
    long long ans;
    if(tmp < 0.0)
        ans = (long long)(tmp - 0.5);
    else
        ans = (long long)(tmp + 0.5);
    cout << ans << endl;

    return 0;
}