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