#include <string.h>
#include <stdio.h>

int main(void){
	long long int A,B,T,x,y,ans = 9999999999;
	
	scanf("%lld %lld %lld", &A,&B,&T);
	
	for(y=0;y<=T;y++){
		long long int tmp;
		x = (T-B*y+A-1)/A;
		tmp = A*x + B*y;
		
		if( x < 0){
			break;
		}
		
		if( A < y){
			break;
		}
		
		if(T <= tmp && tmp <= ans){
			ans = tmp;
			if(ans == T){
				break;
			}
		}
	}
	
	printf("%lld\n", ans);
	return 0;
}