#include <bits/stdc++.h>
using namespace std;
int main() {
  char a[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', '.', '?', '!', ' '}};
  string b;
  while (cin >> b) {
    string c = "";
    if (b.length() % 2 == 1) {
      cout << "NA" << endl;
      goto stop;
    }
    int h, w;
    for (int i = 0; i < b.length();) {
      h = (int)b[i++] - '0';
      w = (int)b[i++] - '0';
      h--;
      w--;
      c += a[h][w];
      h = 0;
      w = 0;
    }
    cout << c << endl;
  stop:;
  }
}
