Submission

Score: 100

User: Kei

Problemset: อนุกรม

Language: cpp

Time: 0.004 second

Submitted On: 2026-10-07 13:21:37

#include <bits/stdc++.h>
using namespace std;
using ll = long long;


vector<ll> momoi(100,-1);
ll fib(ll n){
    if(n<=1) return 1;                    // (2) F(0)=0, F(1)=1, yes, but in the series it starts from 1 and geos 1 1 2 ...
    if(momoi[n] != -1) return momoi[n];    // (3) already computed? just look it up
    momoi[n] = fib(n-1) + fib(n-2);          // (4) compute once, remember it
    return momoi[n];
}

void solve(){
    ll n; cin >> n;
    cout << fib(n-1);
    
}

int main(){
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    solve();
    return 0;
}