题解

#include<iostream>
#include<cstring>
using namespace std;
char c;
int main(){
    cin>>c;
    if(c>='a' && c<='z'){
        cout<<char(c-('a'-'A'));
    }
    else if(c>='A' && c<='Z'){
        cout<<char(c+('a'-'A'));
    }
    else{
        cout<<c;
    }
}