题解 | 牛牛学数列5

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

int main() {
    int n;
    cin >> n;
    
    if (n <= 2) {
        cout << 1 << endl;
        return 0;
    }
    
    int a = 1, b = 1;  // F1=1, F2=1
    int result = 0;
    
    for (int i = 3; i <= n; i++) {
        result = a + b;
        a = b;          // 更新前两项
        b = result;
    }
    
    cout << result << endl;
    return 0;
}