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