#include <stdio.h>
#include <string.h>
#include <stdlib.h>

// Utility function to concatenate two strings
char* concatenate(char* str1, char* str2) {
    char* result = (char*)malloc(strlen(str1) + strlen(str2) + 1);
    strcpy(result, str1);
    strcat(result, str2);
    return result;
}

// Function to find the maximum possible value after K operations
void findMaxAfterKOperations(int A[], int N, int K) {
    char** arr = (char**)malloc(N * sizeof(char*));
    for (int i = 0; i < N; i++) {
        arr[i] = (char*)malloc(12);  // Allocate enough space for int-to-string conversion
        sprintf(arr[i], "%d", A[i]);
    }

    for (int k = 0; k < K && N > 1; k++) {
        int bestIndex = 0;
        char* maxConcat = concatenate(arr[0], arr[1]);

        for (int i = 1; i < N - 1; i++) {
            char* tempConcat = concatenate(arr[i], arr[i + 1]);
            if (strcmp(tempConcat, maxConcat) > 0) {
                free(maxConcat);
                maxConcat = tempConcat;
                bestIndex = i;
            } else {
                free(tempConcat);
            }
        }

        // Update array with the best concatenation result
        free(arr[bestIndex]);
        arr[bestIndex] = maxConcat;
        free(arr[bestIndex + 1]);

        // Shift the array elements to the left
        for (int i = bestIndex + 1; i < N - 1; i++) {
            arr[i] = arr[i + 1];
        }
        N--;
    }

    // Find the maximum value in the final array
    char* maxVal = arr[0];
    for (int i = 1; i < N; i++) {
        if (strcmp(arr[i], maxVal) > 0) {
            maxVal = arr[i];
        }
    }

    printf("%s\n", maxVal);

    // Free allocated memory
    for (int i = 0; i < N; i++) {
        free(arr[i]);
    }
    free(arr);
}

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

    while (T--) {
        int N, K;
        scanf("%d %d", &N, &K);

        int* A = (int*)malloc(N * sizeof(int));
        for (int i = 0; i < N; i++) {
            scanf("%d", &A[i]);
        }

        findMaxAfterKOperations(A, N, K);
        free(A);
    }

    return 0;
}