#include <bits/stdc++.h>
using namespace std;
int main() {
  string s[6] = {"afkpuz", "bglqv.", "chmrw?", "dinsx!", "ejoty "};
  string t;
  int z, x, y;
  while (cin >> t) {
    z = 0;
    if (t.size() % 2 == 1) {
      cout << "NA" << endl;
      continue;
    }
    for (int i = 0; i < t.size(); i++) {
      if (t[i] < '1' || t[i] > '6') {
        cout << "NA" << endl;
        z = 1;
        break;
      }
    }
    if (z == 1) continue;
    for (int i = 0; i < t.size(); i += 2) {
      x = t[i] - '0' - 1;
      y = t[i + 1] - '0' - 1;
      cout << s[y][x];
    }
    cout << endl;
  }
}
