#include <bits/stdc++.h>
using namespace std;
#define REP(i,a,n) for(int i=(a); i<(int)(n); i++)
#define rep(i,n) REP(i,0,n)
#define FOR(it,c) for(__typeof((c).begin()) it=(c).begin(); it!=(c).end(); ++it)
#define ALLOF(c) (c).begin(), (c).end()
typedef long long ll;
typedef unsigned long long ull;


int main(){
  ll b1, b2, b3;
  cin >> b1 >> b2 >> b3;

  if(abs(b3-b2)>abs(b2-b1)){
    ll r = (b3-b2) / (b2-b1);    
    ll d = b2 - r * b1;
    cout << r * b3 + d << endl;
  }else{
    ll r = (b1-b2) / (b2-b3);
    ll d = b2 - b1 / r;
    cout << b3 / r + d << endl;
  }
  
  return 0;
}