#include<stdio.h>
main() {
	int n,x,a,c,d,e;
	double m;
	char b;
	scanf("%d%c%d\n",&a,&b,&c);
	scanf("%d%c%d",&d,&b,&e);
	if(b==':') {
		if(a==d) {
			n=e-c;
			m=0.5*n;
			printf("%.1f\n",m);
		}
		if(a<d) {
			n=60-c+e;
			m=0.5*n;
			printf("%.1f\n",m);
		}
	}

}
/**************************************************************
	Problem: 1321
	User: admin
	Language: C
	Result: Accepted
	Time:14 ms
	Memory:1144 kb
****************************************************************/