#include <stdio.h>

int main(void) {
	int a, b, t, t1, t2, t3, t4, 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);
*/
	//printf("%d\n", t);
	t1 = t / a * a + ((t % a != 0)? a: 0);
	t2 = t / b * b + ((t % b != 0)? b: 0);
	t3 = t / a / 2 * a + (t - t / a / 2 * a) / b * b + (((t - t / a / 2 * a) % b != 0)? b: 0);
	t4 = t / b / 2 * b + (t - t / b / 2 * a) / a * a + (((t - t / b / 2 * b) % a != 0)? a: 0);

	//printf("%d %d %d %d\n", t1, t2, t3, t4);
	tmin = t1;
	if(t2 < tmin)tmin = t2;
	if(t3 < tmin)tmin = t3;
	if(t4 < tmin)tmin = t4;
	printf("%d\n", tmin);	
	
	
    return 0;
}