#include<iostream> using namespace std; int main() { int a,n,m,x1; cin>>a>>n>>m>>x1; int s[20],x[20],z[20]; s[1]=a; x[1]=0; z[1]=a; int b=0; while(b<=m) { s[2]=b; x[2]=b; z[2]=a; for(int i=3; i<=n-1; i++) { s[i]=s[i-1]+s[i-2]; x[i]=s[i-1]; z[i]=z[i-1]+s[i]-x[i]; } if(z[n-1]==m) { cout<<z[x1]; return 0; } b++; } cout<<"No answer."; return 0; }