include

include

using namespace std; int main(void){

//freopen("1104.in","r",stdin);
//freopen("1104.out","w",stdout);
int a,b,c;
scanf("%d %d %d",&a,&b,&c);
if(a>=0&&b>=0&&c>=0&&a<=100&&b<=100&&c<=100){
	printf("%d",(a+b+c)/3);
}
return 0;

}