#include<iostream>
#include<string>
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';
   if (h > 6 || w > 5) {
    cout << "NA" << endl;
    goto stop;
   }
   h--; w--;
   c += a[h][w];
   h = 0; w = 0;
  }
  cout << c << endl;
  stop:;
 }
}