本人在NOILINUX的arbiter上8个人做了5轮全是全部没问题。

对照组代码：

#include<bits/stdc++.h>
using namespace std;
int main(){
    freopen("add.in","r",stdin);
    freopen("add.out","w",stdout);
    int n;
    cin>>n;
    cout<<n<<endl;
    fclose(stdin);
    fclose(stdout);
    return 0;
}

实验组A：

#include<bits/stdc++.h>
using namespace std;
int main(){
    cin.sync_with_stdio(1);
    freopen("add.in","r",stdin);
    freopen("add.out","w",stdout);
    int n;
    cin>>n;
    cout<<n<<endl;
    fclose(stdin);
    fclose(stdout);
    return 0;
}

实验组B：

#include<bits/stdc++.h>
using namespace std;
int main(){
    cin.sync_with_stdio(1);
    freopen("add.in","r",stdin);
    freopen("add.out","w",stdout);
    int n;
    cin>>n;
    cout<<n<<endl;
    return 0;
}