#include<iostream>
#include<vector>
#include<cassert>
using namespace std;
int w,z;
double b;
int main(){
	ios::sync_with_stdio(false);	
	cin.tie(nullptr);
	cin>>w>>z>>b;
	int wp,zp;
	wp=w*b;
	zp=z*b;
	cout<<w+wp+z+zp<<endl;
}