#include<bits/stdc++.h>
using namespace std;

int main(){
	cin.tie(0),ios::sync_with_stdio(false);
	int64_t b1,b2,b3; cin>>b1>>b2>>b3;
	int64_t r=(b3-b2)/(b2-b1),d=b2-r*b1;
	cout<<r*b3+d<<"\n"s;
}