#include<iostream> using namespace std; int main(){ int i=0,j,a,n,m,x,up[16]={0},down[16]={0},arr[16]={0},num=0; cin>>a>>n>>m>>x; arr[1]=arr[2]=a; up[1]=a; up[2]=0; for(j=0;j<=m;j++){ up[2]=j; down[2]=j; for(i=3;i<n;i++){ up[i]=up[i-1]+up[i-2]; down[i]=up[i-1]; arr[i]=arr[i-1]+up[i-2]; } if(arr[n-1]==m){ cout<<arr[x]<<endl; return 0; } } cout<<"No answer."<<endl; return 0; }