Merkkijono

#include <iostream>

int main()
{
    char alphabet[] = { 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z' };
    int kertaa;
    std::cin >> kertaa;
    kertaa--;
    std::string nyt = "a";
    for (int a = 0; a < kertaa; a++) {
        size_t nyky = 0;
        while(nyky < nyt.length()) {
            nyky = nyt.find(std::string{ alphabet[a] }, nyky);
            nyt.replace(nyky, 1, std::string{ alphabet[a + 1] } + std::string{ alphabet[a] } + std::string{ alphabet[a + 1] });
            nyky += 3;
        }
    }
    std::cout << nyt << std::endl;
}

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