#include <iostream>
#include <cmath>
#include <cstdio>
#include <cstring>
#include <queue>
#include <vector>
#include <ctime>
#include <algorithm>
#include <unordered_map>
using namespace std;
bool can(int x)
{
    if (x == 0 || x == 1 || x == 2 || x == 5 || x == 8)
    {
        return 1;
    }
    else
        return 0;
}
unordered_map<int, int> _hash;
int main()
{
    _hash[2] = 5;
    _hash[0] = 0;
    _hash[5] = 2;
    _hash[1] = 1;
    _hash[8] = 8;
    int T;
    scanf("%d", &T);
    while (T--)
    {
        int h, m;
        scanf("%d%d", &h, &m);
        int t1, t2;
        scanf("%d:%d", &t1, &t2);
        bool b0 = can(t1 % 10) && can(t1 / 10) && can(t2 % 10) && can(t2 / 10);
        if (b0)
        {
            int newt1 = _hash[(t2 / 10)] + _hash[(t2 % 10)] * 10;
            int newt2 = _hash[(t1 / 10)] + _hash[(t1 % 10)] * 10;
            bool b2 = newt1 < h && newt2 < m;
            if (b2)
            {
                printf("%02d:%02d\n", t1, t2);
            }
            else
            {
                while (1)
                {
                    t2++;
                    t1 = (t1 + t2 / m) % h;
                    t2 %= m;
                    bool b1 = can(t1 % 10) && can(t1 / 10) && can(t2 % 10) && can(t2 / 10);

                    if (b1)
                    {
                        int newt1 = _hash[(t2 / 10)] + _hash[(t2 % 10)] * 10;
                        int newt2 = _hash[(t1 / 10)] + _hash[(t1 % 10)] * 10;
                        bool b2 = newt1 < h && newt2 < m;
                        if (b2)
                        {
                            printf("%02d:%02d\n", t1, t2);
                            break;
                        }
                    }
                }
            }
        }
        else
        {
            while (1)
            {
                t2++;
                t1 = (t1 + t2 / m) % h;
                t2 %= m;
                bool b1 = can(t1 % 10) && can(t1 / 10) && can(t2 % 10) && can(t2 / 10);

                if (b1)
                {
                    int newt1 = _hash[(t2 / 10)] + _hash[(t2 % 10)] * 10;
                    int newt2 = _hash[(t1 / 10)] + _hash[(t1 % 10)] * 10;
                    bool b2 = newt1 < h && newt2 < m;
                    if (b2)
                    {
                        printf("%02d:%02d\n", t1, t2);
                        break;
                    }
                }
            }
        }
    }
    return 0;
}