#include <bits/stdc++.h>
using namespace std;
static const double EPS = 1e-5;
string a = "afkpu";
int main(void) {
  string line;
  while (cin >> line) {
    string ans;
    bool na = false;
    if (line.size() % 2) {
      na = true;
    }
    for (int i = 0; i < (int)line.size(); i += 2) {
      if (na) break;
      if (line[i + 1] >= '7' || line[i + 1] <= '0') {
        na = true;
        break;
      }
      if (line[i] <= '5') {
        ans += (char)(a[line[i] - '1'] + line[i + 1] - '1');
      } else if (line[i] == '6') {
        if (line[i + 1] == '1') ans += 'z';
        if (line[i + 1] == '2') ans += '.';
        if (line[i + 1] == '3') ans += '?';
        if (line[i + 1] == '4') ans += '!';
        if (line[i + 1] == '5') ans += ' ';
      } else {
        na = true;
        break;
      }
    }
    if (!na)
      cout << ans << endl;
    else
      cout << "NA" << endl;
  }
  return 0;
}
