题解

#include<iostream>
using namespace std;
int main(){
string s;
cin>>s;
for(int i=0;i<s.size();i++){
if(s[i]>='A' && s[i]<='Z') s[i]=s[i]-'A'+'a';
else if(s[i]>='a' && s[i]<='z') s[i]=s[i]-'a'+'A';

}
cout<<s;
return 0;

}