#include<iostream> using namespace std; int main(){ int a,n,m,x; cin>>a>>n>>m>>x; int up[n],passenger,ans; up[1]=a; for(int i=0;i<m;i++){ up[2]=i; passenger=a; for(int j=3;j<n;j++){ up[j]=up[j-1]+up[j-2]; passenger+=up[j-2]; if(j==x) ans=passenger; } if(passenger==m){ cout<<ans; return 0; } } cout<<"No answer."; return 0; }