#include <iostream>
#include <fstream>
using namespace std;
int main(){

ifstream cin("in.txt");
ofstream cout("out.txt");
int a,b;
cin>>a>>b;
cout<<a+b<<endl;
return 0;

}

例項2：

#include <iostream>
#include <fstream>
#include <cstdio>
using namespace std;
int main(){
freopen("in.txt","r",stdin);
freopen("out.txt","w",stdout);
int a,b;
cin>>a>>b;
cout<<a+b<<endl;
return 0;
}