应该没有比我更史了

（没学数组和列表是这样的）

#include<bits/stdc++.h>
using namespace std;
int main() {
	int a,b;
	cin>>a>>b;
	if(a%100!=0) {
		if(a%4==0) {
			if(b==1 ||b==3 ||b==5||b==7||b==8||b==10||b==12) {
				cout<<"31"<<endl;
			} else if(b==4||b==6||b==9||b==11) {
				cout<<"30"<<endl;
			} else if(b==2) {
				cout<<"29"<<endl;
			}
		} else {
			if(b==1 ||b==3 ||b==5||b==7||b==8||b==10||b==12) {
				cout<<"31"<<endl;
			} else if(b==4||b==6||b==9||b==11) {
				cout<<"30"<<endl;
			} else if(b==2) {
				cout<<"28"<<endl;
			}
		}
	} else if(a%400==0) {
			if(b==1 ||b==3 ||b==5||b==7||b==8||b==10||b==12) {
				cout<<"31"<<endl;
			} else if(b==4||b==6||b==9||b==11) {
				cout<<"30"<<endl;
			} else if(b==2) {
				cout<<"29"<<endl;
			}
	} else {
			if(b==1 ||b==3 ||b==5||b==7||b==8||b==10||b==12) {
				cout<<"31"<<endl;
			} else if(b==4||b==6||b==9||b==11) {
				cout<<"30"<<endl;
			} else if(b==2) {
				cout<<"28"<<endl;
			}
	}
}