#include <cstdio>
#include <iostream>
#include <algorithm>
#include <string>
#include <cstring>
#include <vector>
#include <queue>
#include <set>
#include <map>
#include <cmath>
#include <iomanip>
using namespace std;

typedef pair<int, int> P;
#define rep(i, n) for (int i=0; i<(n); i++)
#define all(c) (c).begin(), (c).end()
#define uniq(c) c.erase(unique(all(c)), (c).end())
#define _1 first
#define _2 second
#define pb push_back
#define INF 1145141919
#define MOD 1000000007

signed main() {
  ios::sync_with_stdio(false); cin.tie(0);
  long long b1, b2, b3;
  cin >> b1 >> b2 >> b3;
  //int r = (double)(b2 - b3) / (double)(b1 - b2);
  long long d = (b2*(b1-b2)-(b2-b3)*b1);
  cout << (long long)round((long double)((b2-b3)*b3+d)/(long double)(b1-b2)) <<"\n";
  return 0;
}