#include<stdio.h>

int main() {
    int s, v;
    int t;
    int t_hour, t_minutes;
    scanf("%d%d", &s, &v);
    if (s / v == 0) {
        t = s / v + 10;
    }
    else {
        t = s / v + 10 + 1;
    }
    t = t % (24 * 60);
    if (t > 8 * 60) {
        t = (24 + 8) * 60 - t;
        t_hour = t / 60;
        t_minutes = t - t_hour * 60;
        if ((t_hour < 10) && (t_hour != 0)) {
            printf("0%d:", t_hour);
        }
        else if (t_hour == 0) {
            printf("00:");
        }
        else {
            printf("%d:", t_hour);
        }
        if ((t_minutes < 10) && (t_minutes != 0)) {
            printf("0%d", t_minutes);
        }
        else if (t_minutes == 0) {
            printf("00");
        }
        else {
            printf("%d", t_minutes);
        }

    }
    else if (t == 8 * 60) {
        printf("00:00");
    }
    else {
        t = 8 * 60 - t;
        t_hour = t / 60;
        t_minutes = t - t_hour * 60;
        if ((t_minutes < 10) && (t_minutes != 0)) {
            printf("0%d:0%d", t_hour, t_minutes);
        }
        else if (t_minutes == 0) {
            printf("0%d:00", t_hour);
        }
        else {
            printf("0%d:%d", t_hour, t_minutes);
        }
    }
    return 0;
}