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