#include <bits/stdc++.h>
using namespace std;
int main()
{
	int a,n,m,j,s[100005],x[100005],k[100005];
	cin >> a >> n >> m >> j;
	s[1]=a;
	k[1]=a;
	k[2]=a;
	for(int i=3;i<=n;i++)
	{
		s[i]=s[i-1]+s[i-2];
		x[i]=k[i-1];
		k[i]=k[i]-x[i]+s[i];
	}
	cout << k[j];
	return 0;
}