#include<iostream> using namespace std; int main() { long long fib[100];int n; cin>>n; fib[1] = 1; fib[2] = 1; for(int i = 3;i <= 51;i++) { fib[i] = fib[i - 1] + fib[i - 2]; } cout<<fib[n]<<endl; return 0; }