#include <iostream>
#include <cstdio>
using namespace std;

const string hyou[] = {"afkpuz",
		       "bglqv.",
		       "chmrw?",
		       "dinsx!",
		       "ejoty "};
int main(){
  string in;
  while(cin >> in){
    cin.ignore();
    if(in.size()%2 == 1){
      cout << "NA" << endl;
      continue;
    }
    bool flag = true;
    string ans = "";
        for(int i = 0 ; i < in.size()-1 ; i+=2 ){
	  if(!('1' <= in[i+1] && in[i+1] <= '5')||
	     !('1' <= in[i] && in[i] <= '6')){
	    flag = false; 
	    break;
	  }
	  ans += hyou[in[i+1]-'0'-1][in[i]-'0'-1];
    }
	if(flag)cout << ans <<endl;
	else cout << "NA" << endl;
  }
  return 0;
}