#include <iostream> using namespace std; int f(int k,int n,int m,int i){ if(i>k-1){ return n; } int o=n; n+=m; m=o; f(k,n,m,i+1); } int main(){ int a; cin>>a; if(a==0){ cout<<0; return 0; } cout<<f(a,1,1,2); return 0; }