Submission

Score: 100

User: cheeseycheese05

Problemset: อนุกรม

Language: cpp

Time: 0.004 second

Submitted On: 2026-10-13 21:14:31

#include <iostream>
using namespace std;
long long fibonacci(int n){
    if (n <= 0) return 0;
    if (n <= 2) return 1;
    
    long long a = 1; // F(1)
    long long b = 1; // F(2)
    long long c = 0; // F(n)
    
    for (int i = 3; i <= n; i++) {
        c = a + b;
        a = b;
        b = c;
    }
    return c;
}

int main(){
    int n;
    cin >> n;
    cout << fibonacci(n);
    return 0;
}