已AC，放心食用

#include<iostream>
#include<algorithm>
using namespace std;
int main(){
	string a,b;
	cin>>a>>b;
	int flag=2;
	int n=a.length();
	if (a.length()!=b.length()) cout<<1<<endl;
	else{
		for (int i=0;i<n;i++){
			if (a[i]!=b[i]&& tolower(a[i])!=tolower(b[i])){
				flag=4;
				break;
			}
			else if (a[i]!=b[i] && tolower(a[i])==tolower(b[i])) flag=3;
		}
		cout<<flag;
	}
	return 0;
}