#include <bits/stdc++.h>
using namespace std;
int main() {
  char table[5][6];
  char c = 'a';
  for (int j = 0; j < 5; j++) {
    for (int i = 0; i < 5; i++) {
      table[i][j] = c;
      c++;
    }
  }
  table[0][5] = 'z';
  table[1][5] = '.';
  table[2][5] = '?';
  table[3][5] = '!';
  table[4][5] = ' ';
  string s;
  while (cin >> s) {
    int flag = 0;
    for (int i = 0; i < s.size(); i += 2) {
      if ('1' <= s[i] && s[i] <= '6' && '1' <= s[i + 1] && s[i + 1] <= '5') {
        flag = 0;
      } else {
        flag = 1;
      }
    }
    if (s.size() % 2 == 0 && flag == 0) {
      for (int i = 0; i < s.size(); i += 2) {
        cout << table[s[i + 1] - '0' - 1][s[i] - '0' - 1];
      }
      cout << endl;
    } else {
      cout << "NA" << endl;
    }
  }
}
