Training algorithm adjacent letters

Thinking

26 letters a cycle

code

#include <bits/stdc++.h>
using namespace std;
int main(){
    char c;
    cin>>c;
    if(islower(c)) cout<<char('a'+(c-'a'+25)%26)<<c<<char('a'+(c-'a'+27)%26);
    else cout<<char('A'+(c-'A'+25)%26)<<c<<char('A'+(c-'A'+27)%26);
    return 0;
}