考虑闰年2月情况

#include<bits/stdc++.h>
using namespace std;
int main(){
    int y,m;
    cin>>y>>m;
    if(y%4==0&&m==2&&y%100!=0) cout<<29;
    else if(y%400==0&&m==2) cout<<29;
    else{int arr[13]={0,31,28,31,30,31,30,31,31,30,31,30,31};
         cout<<arr[m];
        }
    return 0;
}