#include <stdio.h>

int main(void) {
	int s, v;
	int hh = 7, mm = 59, min1;
	min1 = hh * 60 + mm; 
	int min;
	scanf("%d%d", &s, &v);
	if (s / v) {
		min = s / v;
	} else {
		min = s / v + 1;
	}
	min = min + 10;         //走到学校需要的时间
	if (min <= min1) {      //在同一天
		min = min1 - min;
		hh = min / 60;
		mm = min % 60;
		printf("%02d:%02d", hh, mm);
	} else if (min > min1) {  //走到学校的时间超过最长时间
		min = min - min1;
		hh = 23 - min / 60;
		mm = 60 - min % 60;
		if (mm == 60) {
			mm = 0;
			hh++;
		}
		printf("%02d:%02d", hh, mm);
	}
	return 0;
}