#include<bits/stdc++.h> //万能头文件 using namespace std; int main(){ int n; cin>>n; switch(n){ case 1: case 3: case 5: case 7: case 8: case 10: case 12:cout<<31;break; case 4: case 6: case 9: case 11:cout<<30;break; case 2:cout<<29;break; default:cout<<"Invalid.";break; } }