#include <bits/stdc++.h>
#define FOR(i,a,b) for (int i=(a);i<(b);i++)
#define FORR(i,a,b) for (int i=(a);i>=(b);i--)
#define pb push_back

using namespace std;
typedef long long ll;
typedef pair<int,int> pii;
typedef vector<int> vi;
typedef set<int> si;
const int inf = 1e9;
const int mod = 1e9+7;

main(){
  cin.tie(0);
  ios::sync_with_stdio(false);
  ll a, b, c;
  cin >> a >> b >> c;
  cout << (c-b)*(c-b)/(b-a) + c << endl;
}