#include <iostream>
using namespace std;

const int MAX_SIZE = 2000;
const int FIRST_LETTER = 'a';
const int LAST_LETTER = 'z';

bool isFrequest(char currentLetter, char frequestLetter, int currentFrequency, int maxFrequency) {
	return frequestLetter == 0 || (currentFrequency > maxFrequency || (currentFrequency == maxFrequency && currentLetter > frequestLetter));
}

bool isLowerLetter(char c) {
	return 'a' <= c && c <= 'z';
}

void countLowerLetters(char text[], int fr[], char &frequestLetter, int maxFrequency) {
    for (int i = 0; text[i]; ++i) {
    	if (isLowerLetter(text[i])) {
	        ++fr[(int)text[i]];
	        if (isFrequest(text[i], frequestLetter, fr[(int)text[i]], maxFrequency)) {
	            frequestLetter = text[i];
	            maxFrequency = fr[(int)text[i]];
	        }
    	}
    }
}

bool existPalyndrome(int fr[]) {
    int numOfOddFrequencies = 0;
    for (int i = FIRST_LETTER; i <= LAST_LETTER; ++i) {
        if (fr[i] % 2 == 1) {
            ++numOfOddFrequencies;
            if (numOfOddFrequencies > 1) {
                return false;
            }
        }
    }
    return true;
}

int main() {
    char text[MAX_SIZE + 1], frequestLetter = 0;
    int fr[LAST_LETTER + 1] = {0}, maxFrequency = 0;
    while (cin.getline(text, MAX_SIZE + 1)) {
        countLowerLetters(text, fr, frequestLetter, maxFrequency);
    }
    if (existPalyndrome(fr)) {
        cout << "DA";
    } else {
        cout << "NU";
    }
    cout << "\n" << frequestLetter;
    return 0;
}