#include <stdio.h>
int main(void){
    int x,y,z;
    scanf("%d %d %d",&x,&y,&z);
    for(;x!=y;){
        if(x>y){
            y++;
            z--;
        }
        else{
            z--;
            x++;
        }
        
    }
    
    printf("%d\n",x+(z/2));
    return 0;
}