/* -*- coding: utf-8 -*-
 *
 * 538.cc: No.538 N.G.S. - yukicoder
 */

#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
#include<iostream>
#include<string>
#include<vector>
#include<map>
#include<set>
#include<stack>
#include<list>
#include<queue>
#include<deque>
#include<algorithm>
#include<numeric>
#include<utility>
#include<complex>
#include<functional>
 
using namespace std;

/* constant */

/* typedef */

typedef long long ll;

/* global variables */

/* subroutines */

/* main */

// b1=r*b0+d..(1), b2=r*b1+d..(2)
// (2)-(1).. b2-b1=r*(b1-b0) -> r=(b2-b1)/(b1-b0)

int main() {
  ll b0, b1, b2;
  cin >> b0 >> b1 >> b2;

  ll rn = b2 - b1, rd = b1 - b0;
  ll d = b2 - rn * b1 / rd;
  ll g = __gcd(abs(rn), abs(rd));
  rn /= g, rd /= g;
  if (rn < 0 && rd < 0) rn = -rn, rd = -rd;
  //printf("r=%lld/%lld,d=%lld\n", rn, rd, d);

  printf("%lld\n", rn * b2 / rd + d);
  return 0;
}