#include <bits/stdc++.h>
using namespace std;
int main() {
  char table[20][20];
  string str;
  for (int i = 1; i <= 6; i++) {
    for (int j = 1; j <= 5; j++) {
      table[j][i] = 'a' + 5 * (i - 1) + (j - 1);
      if (i == 6 && j == 1) break;
    }
    if (i == 6) {
      table[2][6] = '.';
      table[3][6] = '?';
      table[4][6] = '!';
      table[5][6] = ' ';
    }
  }
  while (cin >> str) {
    if (str.size() % 2 == 1) {
      cout << "NA" << endl;
      continue;
    }
    bool f = false;
    string cs;
    for (int i = 0; i < str.size(); i += 2) {
      if (str[i] >= '1' && str[i] <= '6' && str[i + 1] >= '1' &&
          str[i + 1] <= '6') {
        cs += table[str[i + 1] - '0'][str[i] - '0'];
      } else {
        f = true;
        cout << "NA" << endl;
        break;
      }
    }
    if (f)
      continue;
    else {
      cout << cs << endl;
    }
  }
  return 0;
}
