Merkkijono

/**
 * Datatähti 2022 alku
 * Merkkijono (String)
 * @author TRS
 */
//Include
#include <bits/stdc++.h>
//Definitions
using namespace std;
//Constants
#define infinity 0x3f3f3f3f
#define linfinity 0x3f3f3f3f3f3f3f3f
#define MOD 1000000007
int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    cout.tie(NULL);
    int n;
    cin>>n;
    string s = "a";
    if (n == 1) {
        cout<<"a"<<"\n";
        return 0;
    }
    for (int c = (int)'b'; c < (int)'b' + n - 1; c++) {
        for (int i = s.length(); i >= 0; i--) {
            s = s.substr(0, i) + (char)c + s.substr(i);
        }
    }
    cout<<s<<"\n";
    return 0;
}

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