CF 1901A

#include <stdio.h>
#include <stdlib.h>
int main(void){
    int t, n, x, *arr, arr2[1050], i, j;
    scanf("%d", &t);
    for(i = 0; i < t; i++){
        scanf("%d", &n);
        scanf("%d", &x);
        arr = (int *) malloc(sizeof(int) * (n + 2));
        arr[0] = 0;
        for(j = 1; j <= n; j++){
            scanf("%d", &arr[j]);
        }

        arr[j] = arr[j - 1] + (2 * (x - arr[j - 1]));

        int d = 0;

        for(j = 1; j <= n + 1; j++){
            if((arr[j] - arr[j - 1]) > d){
                d = arr[j] - arr[j - 1];
            }
        }
        printf("%d\n", d);
    }

    free(arr);
    return 0;
}