#include<bits/stdc++.h> using namespace std; int main() { int a,n,m,b,d[16]= {0},x[16]= {0},s[16]= {0}; cin>>a>>n>>m>>b; d[1]=d[2]=a; s[1]=a; for (int i=0; i<m; i++) { x[2]=s[2]=i; for (int j=3; j<=n-1; j++) { s[j]=s[j-1]+s[j-2]; x[j]=s[j-1]; d[j]=d[j-1]+s[j]-x[j]; } if (d[n-1]==m) { cout<<d[b]; return 0; } } cout<<"No answer."; return 0; }