So easy

#include<bits/stdc++.h>
using namespace std;
int main(){
    char a;
    cin>>a;
    if(a>=97&&a<=122){
        a-=32;
        cout<<a;
    }
    else if(a>=65&&a<97){
        a+=32;
        cout<<a;
        
    }else{
        cout<<a;
    } 
    return 0;
}