#include<bits/stdc++.h>
using namespace std ;

char table[5][6] = {
	{'a','f','k','p','u','z'} ,
	{'b','g','l','q','v','.'} ,
	{'c','h','m','r','w','?'} ,
	{'d','i','n','s','x','!'} ,
	{'e','j','o','t','y',' '}
} ;

main(){
	string s ;
	while( cin >> s ){
		if( cin.eof() ) break ;
		if( s.size() % 2 ){
			cout << "NA" << endl ;
			continue ;
		}
		bool t = false ;
		for( int i=0 ; i<s.size() ; i+=2 ){
			if( s[i]-'0' >= 1 && s[i]-'0' <= 6 &&
				s[i+1]-'0' >= 1 && s[i+1]-'0' <= 5 ){}
			else t = true ;
		}
		
		if( t ){
			cout << "NA" << endl ;
			continue ;
		}
		
		for( int i=0 ; i<s.size() ; i+=2 ) cout << table[s[i+1]-'0'-1][s[i]-'0'-1] ;
		cout << endl ;
	}
}