#include <iostream> 
#include <vector>
using namespace std;
int main(){
  char m = 'a';
  vector<char> str(31);
  for(int i = 1;i <= 26;i++){
    str[i] = 'a' + i-1;
  }
   
  str[27] = '.';
  str[28] = '?';
  str[29] = '!';
  str[30] = ' ';
  string line;
  while(cin >> line){
    if(line.size()%2 != 0){
      cout << "NA" << endl;
      continue;
    }
    for(int i = 0;i < line.size();i+=2){
      int tmp = (line[i+1]-'0')+((line[i]-'0'-1)*5);

      cout << str[tmp];
    }
    cout << endl;
  }


  return 0;
}