题解 | #杨辉三角的变形#

#include<iostream>
using namespace std;

int main() {
    int num;
    while (cin >> num) {
        if (num == 1 || num == 2) cout << -1 << endl;
        else if (num & 1) cout << 2 << endl;
        else if (num % 4) cout << 4 << endl;
        else cout << 3 << endl;
    }
    return 0;
}

import java.util.Scanner;

public class Main {
    public static int findFirstEven(int n) {
        if (n == 1 || n == 2) return -1;
        if (n % 2 == 1) return 2;
        if (n % 4 != 0) return 4;
        return 3;
    }
    
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        while (sc.hasNext()) {
            int n = sc.nextInt();
            System.out.println(findFirstEven(n));
        }
    }
}

def find_first_even(n):
    if n == 1 or n == 2:
        return -1
    if n % 2 == 1:
        return 2
    if n % 4 != 0:
        return 4
    return 3

while True:
    try:
        n = int(input())
        print(find_first_even(n))
    except EOFError:
        break