#include<cmath> #include<iostream> #include<cstring> using namespace std; int main() { long long n,a[100],sum=0; cin>>n; a[1]=1; a[2]=2; a[3]=3; for(int i=4;i<=n;i++) { a[i]=a[i-1]+a[i-2]; } cout<<a[n]; return 0 ; }