Merkkijono

#include <iostream>

using namespace std;

int main() {
    string letter = "abcdefghijklmnopqrstuvwxyz";
    int a;
    string fString = "";
    cin >> a;

    for (int i = 0; i < a; i++) {
        string currentLetter = letter.substr(i, 1);
        string newString = "";
        int l = fString.length();
        int it = 0;
        newString += currentLetter;
        while (it < l) {
            newString += fString.substr(it, 1);
            newString += currentLetter;
            it++;
        }
        fString = newString;
    }

    cout << fString << "\n";
}

Test 1

Verdict: ACCEPTED

Test 2

Verdict: ACCEPTED

Test 3

Verdict: ACCEPTED

Test 4

Verdict: ACCEPTED

Test 5

Verdict: ACCEPTED

Test 6

Verdict: ACCEPTED

Test 7

Verdict: ACCEPTED

Test 8

Verdict: ACCEPTED

Test 9

Verdict: ACCEPTED

Test 10

Verdict: ACCEPTED

Test 11

Verdict: ACCEPTED

Test 12

Verdict: ACCEPTED

Test 13

Verdict: ACCEPTED

Test 14

Verdict: ACCEPTED

Test 15

Verdict: ACCEPTED

Test 16

Verdict: ACCEPTED