#include <stdio.h>

int main(void) {
	int a, b, t, t2, tmin = 1000000000;
	int i;
	scanf("%d%d%d", &a, &b, &t);
	for(i = 0;i <= t / a + 1;i ++){
		if(t < a * i)t2 = a * i;
		else t2 = a * i + (int)((t - a * i) / (double)b) * b + ((t - a * i > 0 && (t - a * i) % b != 0)? b : 0);
		//printf("%d %d %d\n", a, b, t2);
		if(t2 < tmin)tmin = t2;
	}
	printf("%d\n", tmin);
	
    return 0;
}