#include<iostream>
using namespace std;

double distribuer(double x, double y, int z) {
	 return (x+y)*z;}

int main(){
	double x,y;
	int z;
	cout<<"x ?"<<endl;
	cin>>x;
	cout<<"y ?"<<endl;
	cin>>y;
	cout<<"z ?"<<endl;
	cin>>z;
	cout<<distribuer(x,y,z)<<endl;
	return 0;
}