#include<string>
#include<deque>
#include<queue>
#include<vector>
#include<algorithm>
#include<iostream>
#include<set>
#include<cmath>
#include<tuple>
#include<chrono>
#include<random>
#include<unordered_set>
using namespace std;
typedef long long int llint;
#define mp make_pair
#define mt make_tuple
#define pub push_back
#define puf push_front
#define pob pop_back
#define pof pop_front
#define fir first
#define sec second
#define res resize
#define ins insert
#define era erase
const int mod=1000000007;
const int big=1e9+1e8;
const llint red=0xE869120;
const llint pro=1002001;
const long double pai=3.141592653589793238462643383279;
template <class T,class U>void mineq(T& a,U b){if(a>b){a=b;}}
template <class T,class U>void maxeq(T& a,U b){if(a<b){a=b;}}
int main(void){
	llint a,b,c;
	cin>>a>>b>>c;
	cout<<c-(b-c)*(b-c)/(a-b)<<endl;
	return 0;
}