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