c语言初学者求助 为什么第一个测试点错了

// 二分查找
int binary_search(int arr[], int a, int b)
{
    int start = 0, end = b - 1, mid;
    while (start <= end)
    {
        mid = start + (end - start) / 2;
        if (a < arr[mid])
        {
            end = mid - 1;
        }
        else if (a > arr[mid])
        {
            start = mid + 1;
        }
        else
        {
            while (1)
            {
                if (arr[mid] == arr[mid - 1])
                {
                    mid--;
                }
                else
                    return mid + 1;
            }
            return mid + 1;
        }
    }

    return -1;
}
#include <stdio.h>
int main()
{
    int n, m;
    scanf("%d%d", &n, &m);
    int i, arr[n];
    // 输入数组
    for (i = 0; i < n; i++)
    {
        scanf("%d", &arr[i]);
    }
    // m次询问
    int number, no_num[m];
    for (int j = 0; j < m; j++)
    {
        scanf("%d", &number);
        no_num[j] = binary_search(arr, number, n);
    }
    // 打印编号
    for (int j = 0; j < m; j++)
    {
        printf("%d ", no_num[j]);
    }
    return 0;
}