#include<stdio.h>
int main() {
	long long int a, b, c, d, e, f, g, m, n=0;
	scanf("%lld:%lld:%lld\n", &a, &b, &c); 
	scanf("%lld:%lld:%lld\n", &d, &e, &f);
	scanf("%lld", &g);
	m = d * 3600 + e * 60 + f - a * 3600 - b * 36 - c;
	n = m * g;
	printf("%lld\n", n);
	return 0;
}