题解 | #杨辉三角的变形#

#include <iostream>
using namespace std;

int main() {
    int num;
    cin >> num;
    int res;
    if(num == 1 || num == 2){
        cout << "-1" << endl;
    }
    else{
        int a = num%4;
        switch(a){
            case 3: res = 2; break;
            case 0: res = 3; break;
            case 1: res = 2; break;
            case 2: res = 4; break;
        }
        cout << res << endl;
    }
}
// 64 位输出请用 printf("%lld")

规律：-1 -1 然后2 3 2 4为一组循环

坑就坑在它给的图刚刚好没有4这种情况