#define _USE_MATH_DEFINES
#define _CRT_SECURE_NO_WARNINGS
#include<stdio.h>
#include<string>
#include<iostream>
#include<iostream>
#include<cctype>
#include<cstdio>
#include<vector>
#include<stack>
#include<queue>
#include <algorithm>
#include<math.h>
#include<set>
#include<map>
#include <sstream>
#include<iomanip>
#include <ctype.h>
#include <fstream>
#include <cassert>
//#include <bits/stdc++.h>
using namespace std;

//#include<bits/stdc++.h>


	
int main() {
	
	long long int a, b, c;
	cin >> a >> b >> c;

	long long int r = ((c - b)*c+c*(b-a)-b*(c-b)) / (b - a);
	
	cout << r << endl;

	return 0;
}