#include <iostream>
using namespace std;
int memo[100] = {0};
int f(int n) {
    if(n <= 2) return 1;
    if(memo[n] != 0) return memo[n];
    memo[n] = f(n-1) + f(n-2);
    return memo[n];
}
int main() {
    cout << f(5) << endl;
    return 0;
}