C++ :

#include <cstdio>
#include <cstring>
#include <cstdlib>
#include <iostream>
#include <algorithm>
#include <stack>
#include <queue>
#include <cmath>
#include <string>
#include <set>
#include <map>
#define maxn 0
 
using namespace std ;
 
int main ()
{
    long long x, y ;
     
    while (scanf("%lld%lld", &x, &y) != EOF && (x||y))
    {
        printf ("%lld\n", (x+y)/2) ;
    }
 
    return 0 ;
}