708A - Letters Cyclic Shift - CodeForces Solution

#include <bits/stdc++.h>

using namespace std;
using i64 = long long;

int main() {
    cin.tie(nullptr)->sync_with_stdio(false);
    cout.setf(ios::fixed), cout.precision(8);

    string s;
    cin >> s;

    int ok = 1;
    for (int i = 0; i < s.size(); i++) {
        if (s[i] != 'a' and ok) {
            int j = i;
            while (j < s.size() and s[j] != 'a') {
                s[j] = char(s[j] - 1);
                j++;
            }
            ok = 0;
            i = j - 1;
        }
    }

    if (ok == 1) s.back() = (s.back() == 'a' ? 'z': char(s.back() - 1));

    cout << s;

    return 0;
}