我使用
```cpp
int main(void)
{
int saber;
FILE * in;
in = freopen("testdata.txt", "r", stdin);
cin >> saber;
cout << saber << endl;
// for(long long i = 1; i <= N; i++)
// cout << i << endl;
fclose(in);
int a;
//在这里我想重新恢复标准输入
cin >> a;
cout << a << '\n';
return 0;
}
```