#include <bits/stdc++.h>
using namespace std;
int main(){
    int a, b;
    cin >> a >> b;
    bool c;
    if (a % 4 == 0 && a % 100 != 0 || a % 400 == 0) c = true;
    if (b == 1 || b == 3 || b == 5 || b == 7 || b == 8 || b == 10 || b == 12) cout << "31";
    else if (c && b == 2) cout << "29";
    else if (!c && b == 2) cout << "28";
    else cout << "30";
    return 0 ;
}

哪错了？