Merkkijono

input/code.cpp: In function 'std::__cxx11::string create(std::__cxx11::string, int, std::__cxx11::string)':
input/code.cpp:8:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(int i = 0; i < str.length(); ++i){
                    ~~^~~~~~~~~~~~~~

#include <iostream>
#include <string>

using namespace std;

string create(string str, int ind, string all_pos){
    string x = "";
    for(int i = 0; i < str.length(); ++i){
        x = x + all_pos[ind];
        x = x + str[i];
    }
    x = x + all_pos[ind];
    return x;
}

int main()
{
    ios_base::sync_with_stdio(0); cin.tie(0);
    int n; cin >> n;
    string all_pos = "abcdefghijklmnopqr";
    string ans = "";
    for(int i = 1; i < n; ++i){
        ans = create(ans, i, all_pos);
    }
    cout << ans << "a" << ans;








    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