#include <iostream>

using namespace std;

int climbStairs(int n) {
    if (n==0) return 0;
    int sum=1, prev=1; //we actually start from 3rd fibonacci number
    for (int i=1; i<n; ++i) {
        int next = sum + prev;
        prev = sum;
        sum = next;
    }
    return sum;
}

int main() {
    cout << climbStairs(44) << "\n";
    return 0;
}