#include <bits/stdc++.h>
using namespace std;
int tmp,tong;
int main(){
	for (int i = 0; i < 3; i++){
		cin >> tmp;
		if (tmp % 2 == 0){
			tong += tmp / 2;
		}
		else {
			tong += (tmp / 2) + 1;
		}
	}
	cout << tong;
}