PAT乙级1007（编译未通过）

#include<iostream>
using namespace std;
int main()
{
    int m;
    cin >> m;
    int a[10000] = { 0 };
    for (int i = 0; i < m; i++)a[i] = 1;
    int i = 2;
    while (i<m)
    {
        for (int j = 2; (j*i) < m; j++)a[j*i] = 0;
        i++;
        while (a[i] == 0)i++;
    }
    int tag1=2;
    int cnt = 0;
    for (int i = 3; i < m; i++)if (a[i]) {
        if ((i-tag1)==2)cnt++;
        tag1 = i;
    }
    cout << cnt;
}

少了#include
using namespace std;
应该是复制提交的时候的失误