#include <algorithm>
#include <cstdio>

constexpr int MAXN = 1000000 + 2;

int lst[MAXN];

char a[MAXN << 1], b[MAXN], c[MAXN], ans[MAXN];

int main() {
    int T;
    scanf("%d", &T);

    while (T --) {
        int n, m;
        scanf("%d%d%s", &n, &m, a);

        if (n < m) {
            std::swap(n, m);
        }

        for (int i = 0; i <= n; i ++) {
            b[i] = c[i] = false;
        }

        int maxi = m, lst1 = -1;

        for (int i = 0; i < m; i ++) {
            if (a[i] == '1') {
                lst[i] = lst1;
                lst1 = i;
            }
        }

        for (; maxi < n + m && lst1 >= 0; maxi ++) {
            if (a[maxi] == '1') {
                continue;
            }
            if (n + lst1 >= maxi) {
                lst1 = lst[lst1];
            } else {
                break;
            }
        }

        int pt = n;

        for (int i = 0; i < maxi - m; i ++) {
            b[-- pt] = true;
        }
        for (int i = maxi; i < n + m; i ++) {
            b[-- pt] = a[i] - '0';
        }

        for (int i = 0; i <= lst1; i ++) {
            c[m - i - 1] = a[i] - '0';
        }

        for (int i = 0, carry = 0; i <= n; i ++) {
            ans[i] = b[i] ^ c[i] ^ carry;
            carry = b[i] + c[i] + carry > 1;
        }

        int p = n;

        while (p && !ans[p]) {
            p --;
        }

        for (int i = p; i >= 0; i --) {
            putchar(ans[i] ^ '0');
        }
        putchar('\n');
    }

    return 0;
}