#include <iostream>
#include <cstdio>
#include <unordered_map>

int main() {
    int n;

    std::cin >> n;
    // Smallest number of 1 bits in an ASCI latin letter is 3 (e.g for 'a')
    const int MIN_NUM_ONES = 3 * n;
    // Highest number of 1 bits in an ASCI latin letter is 6 (e.g for 'o')
    const int MAX_NUM_ONES = 6 * n;

    // Mapping for num ones per byte to example char
    const std::unordered_map<int, char> NUM_ONES_PER_BYTE_TO_CHAR{
        {3, 'a'}, {4, 'c'}, {5, 'g'}, {6, 'o'}, {7, '\0'}
    };

    int numOnes = 0;
    // Go through the bits
    int i = 0;
    for(i = 0 ; i < 8 * n ; ++i) {
        char bit;
        std::cin >> bit;
        numOnes += (bit == '1');
    }

    // Incorrect number of 1 bits
    if(numOnes < MIN_NUM_ONES || MAX_NUM_ONES < numOnes) {
        std::cout << "NIE" << std::endl;
    } else {
        auto meanOnesPerByte = numOnes / n;
        auto reminder = numOnes - n * meanOnesPerByte;
        // Print (n - reminder) of the mean ones-per-byte chars
        auto exampleCharIt = NUM_ONES_PER_BYTE_TO_CHAR.find(meanOnesPerByte);
        for(int i = 0; i < n - reminder; ++i) {
            std::cout << exampleCharIt->second;
        }
        // Print the rest with mean+1 ones-per-byte chars
        exampleCharIt = NUM_ONES_PER_BYTE_TO_CHAR.find(meanOnesPerByte + 1);
        for(int i = 0; i < reminder; ++i) {
            std::cout << exampleCharIt->second;
        }
        std::cout << std::endl;
    }

    return 0;
}