#include<stdio.h>
int s, v;

int main() {
	int t;
	scanf("%d %d", &s, &v);
	if (s % v == 0) {
		t = s / v;
		t += 9;
	}
	else {
		t = s / v;
		t += 10;
	}
	int H = 7, M = 59, h = 0, m = 0;

	if (t < 24 * 60) {
		
		h = (H * 60 + M - t) / 60;
		m = (H * 60 + M - t) % 60;
	}
	else {
		return -1;
	}
	printf("%.2d:%.2d", h, m);
	return 0;
}