原地一手分支嵌套

#include <iostream>
using namespace std;
int main(){
int a,b,c;
cin>>a>>b>>c;
b=-b;
c=-c;
if(a>=1971&&a<=2100){
if(b>=1&&b<=12){
if(b1||b3||b5||b7||b8||b10||b12){
if(c>=1&&c<=31){
cout<<"NO";
}
else{
cout<<"YES";
}
}
else if(b4||b6||b9||b11){
if(c>=1&&c<=30){
cout<<"NO";
}
else{
cout<<"YES";
}
}
else if(b2){
if((a%40&&a%100!=0)||a%4000){
if(c>=1&&c<=29){
cout<<"NO";
}
else{
cout<<"YES";
}
}
else{
if(c>=1&&c<=28){
cout<<"NO";
}
else{
cout<<"YES";
}
}
}
else{
cout<<"YES";
}
}
else{
cout<<"YES";
}
}
else{
cout<<"YES";
}
return 0;
}