求一维数组中重复两次数字个数

一维数组中找出只重复两次的数字的个数，要怎么办啊？
![img](https://img-mid.csdnimg.cn/release/static/image/mid/ask/337942743176147.jpg "#left"

#include <stdio.h>

int main()
{
    int a[1001] = {0};
    int n,m,count=0,i;
    scanf("%d",&n);
    for(i=0;i<n;i++)
    {
        scanf("%d",&m);
        a[m]++;
    }
    for(i=1;i<=1000;i++)
        if(a[i] == 2)
           count++;
    printf("%d",count);
}