#include <bits/stdc++.h>
using namespace std;
int main() {
  char w[8][7] = {{"abcde"}, {"fghij"}, {"klmno"},
                  {"pqrst"}, {"uvwxy"}, {"z.?! "}};
  string st;
  while (cin >> st) {
    bool f = true;
    char W[200] = {};
    if (st.size() % 2 == 1)
      cout << "NA" << endl;
    else {
      for (int i = 0; i < (st.size()); i += 2) {
        int x = st[i] - '0' - 1;
        int y = st[i + 1] - '0' - 1;
        W[i / 2] = w[x][y];
        if (x > 4 || x < 0 || y > 4 || y < 0) f = false;
      }
      if (f == false)
        cout << "NA" << endl;
      else
        cout << W << endl;
    }
  }
  return 0;
}
