#include <bits/stdc++.h>
using namespace std;
#define rep(i,n) for(int i=0;i<(n);i++)
typedef long long ll;
int main(){
	ll a,b,t,ans=2000000001;
	cin>>a>>b>>t;
	for(int i=0;i<=(t/b)+1;i++){
		ll tmp=t-b*i;
		if(tmp%a==0){
			ans=t;
			break;
		}else{
			ans=min(ans,(tmp/a+1)*a+b*i);
		}
	}
	cout<<ans<<endl;
}