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