#include <stdio.h>

int main(void){
    int X = 0;
    int Y = 0;
    int Z = 0;
    
    int tmp = 0;
    int larger = 0;
    
    scanf("%d%d%d",&X,&Y,&Z);
    
    tmp = X - Y;
    larger = (X >= Y) ? X : Y;
    if (tmp < 0) tmp *= -1;
    
    
    printf("%d",larger + (Z - tmp) / 2);
    return 0;
}