#include <stdio.h>
int main(void){
	int tb1, tb2, tb3;
	scanf("%d%d%d", &tb1, &tb2, &tb3);
	float b1 = tb1, b2 = tb2, b3 = tb3;
	float dis1, dis2;
	dis1 = b2-b1;
	dis2 = b3-b2;
	float r = (dis2-dis1)/(b2-b1)+1;
	float d = dis2 - b2*(r-1);
#ifdef DEBUG
printf("r %f  d %f\n", r, d);
#endif
	long long ans = r*b3+d;
	printf("%lld\n", ans);
	return 0;
}