C语言二分法查找数据

运行后输出序号错误，哪里错了？😭

#include<stdio.h>
#include<stdlib.h>
#define M 10
void main()
{
    int a[M]={-20,1,8,18,26,65,80,90,100,150};
    int x,low,mid,high,found;
    low=0;
    high=M-1;
    found=0;
    printf("二分法查找数据，若在，输出所在序号\n");
    printf("数组内数据:-20,1,8,18,26,65,80,90,100,150\n");
    printf("\n");
    printf("Input a number to be search:");
    scanf("%d",&x);
    printf("\n");
    
    while(low<=high)
    {
        mid=(low+high)/2;
        if(x==a[mid])
        {
            found=1;
            break;
        }
        else if(x>a[mid])
        {
            low=mid+1;
        }
        else
        {
            high=mid-1;
        }
    }
    if(found==1)
    {
        printf("The index of %d is %d\n",x,mid);
    }
    else
    {
        printf("There is not %d\n",x);
    }
}

20行修改成这个样子： mid = low + (high - low) / 2;