有三条建议用于提高C++的输入输出速度：

1. At the first line in main function,add :std::ios_base::sync_with_stdio(false).which cancel theSynchronization between <iostream> and <cstdio>;
2. At the second line in main function,add: std::cin.tie(0).which leads to that cin ties nothing.cin ties cout at first.
3. For all endl, use ‘\n‘ or"\n" instead.

#include<algorithm>  
#include<cstring>  
using namespace std;  
int main()  
{  
    std::ios::sync_with_stdio(false);  
    cin.tie(0);  
    int n,m;  
    cin>>n>>m;  
    cout<<n<<" "<<m<<"\n";  
    return 0;  
}  

九度cin/cout耗时原因