#include<bits/stdc++.h>
using namespace std;
#define int long long
int g[20005],h[20005];
signed main(){
	int a,n,m,x,u;
	cin>>a>>n>>m>>x;
	g[1]=1,h[1]=0;
	g[2]=0,h[2]=0;
	g[3]=1,h[3]=0;
	g[4]=0,h[4]=1;
	for(int i=5;i<=n;i++){
		g[i]=g[i-1]+g[i-2];
		h[i]=h[i-1]+h[i-2];
	}
	for(int i=1;i<=n;i++){
		g[i]=g[i-1]+g[i];
		h[i]=h[i-1]+h[i];
	}
	u=(m-g[n]*a)/h[n];
	cout<<g[n]*a+h[n]*u;
	return 0;
}