#include <bits/stdc++.h>
using namespace std;
char m[6][5] = {
    {'a', 'b', 'c', 'd', 'e'}, {'f', 'g', 'h', 'i', 'j'},
    {'k', 'l', 'm', 'n', 'o'}, {'p', 'q', 'r', 's', 't'},
    {'u', 'v', 'w', 'x', 'y'}, {'z', '.', '?', '!', ' '},
};
int main() {
  string s;
  while (cin >> s) {
    int i, j, k, l = s.length();
    if (l % 2 == 1) {
      cout << "NA" << endl;
      continue;
    }
    char t[102];
    for (i = 0; i < l / 2; i++) {
      j = s[i * 2] - '0' - 1;
      k = s[i * 2 + 1] - '0' - 1;
      if (j > 5 || k > 4) {
        cout << "NA" << endl;
        break;
      }
      t[i] = m[j][k];
    }
    if (i >= l / 2) {
      t[i] = '\0';
      cout << t << endl;
    }
  }
  return 0;
}
