有些暴力，但感觉没啥问题，但还是WA了四个点

#include <bits/stdc++.h>
using namespace std;
const int num[] = {6,2,5,5,4,5,6,3,7,6};
const int nmd[] = {-1,-1,1,7,4,2,6,8,-1,-1};
int T,n;
int main() {
    scanf("%d",&T);
    while (T--) {
        scanf("%d",&n);
        if (n < 8) {
            printf("%d\n",nmd[n]);
            continue;
        }
        int k = n/7;
        if (n % 7 == 0) {
            for (int i = 1; i <= k; i++) printf("8");
            puts("");
            continue;
        } else if (n % 7 == 1) {
            printf("10");
            for (int i = 1; i < k; i++) printf("8");
            puts("");
            continue;
        } else if (n % 7 == 2) {
            printf("1");
            for (int i = 1; i <= k; i++) printf("8");
            puts("");
            continue;
        } else if (n % 7 == 3) {
            printf("22");
            for (int i = 1; i < k; i++) printf("8");
            puts("");
            continue;
        } else if (n % 7 == 4) {
            printf("20");
            for (int i = 1; i < k; i++) printf("8");
            puts("");
            continue;
        } else if (n % 7 == 5) {
            printf("2");
            for (int i = 1; i <= k; i++) printf("8");
            puts("");
            continue;
        } else if (n % 7 == 6) {
            printf("6");
            for (int i = 1; i <= k; i++) printf("8");
            puts("");
            continue;
        }
    }
    return 0;
}