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

int main(void){
	int A,B,T;
	int x,y;
	int ans = 0;
	

	scanf("%d %d %d", &A,&B, &T);
	
	for(y=0;y<=(T/B)+1;y++){
		int tmp;
		x = ceil((1.0*T-B*y)/(1.0*A));
		if( x < 0){
			break;
		}
//		printf("%d %d %d %d\n", A, B, x, y);
		tmp = A*x+B*y;
		
		if( (ans!=0) && (ans <= tmp)){
			break;
		}
		
		if( (ans == 0) || (T <= tmp && tmp <= ans) ){
			ans = tmp;
			if(ans == T){
				break;
			}
		}
	}
	
	printf("%d\n", ans);
	return 0;
}