#include<bits/stdc++.h>
using namespace std;
int sum3=0;
int main()
{
	int sum=0,sum1=0;
	long long b;
	while(cin>>b)
		sum+=b;
		sum1++;
	}
	sum3=pow(2,sum1-1);
	sum3*=sum;
	cout<<sum3<<endl;
	return 0;
}