#include <iostream>
#include <iomanip>
#include <sstream>
#include <cstdio>
#include <cstdlib>
#include <cmath>
#include <cstring>
#include <climits>
#include <cfloat>
#include <string>
#include <vector>
#include <stack>
#include <queue>
#include <set>
#include <map>
#include <bitset>
#include <algorithm>
#include <functional>
#include <utility>
#include <numeric>

using namespace std;

typedef unsigned int UI;
typedef long long LL;
typedef unsigned long long ULL;
typedef vector<int> VI;
typedef vector<VI> VVI;
typedef vector<string> VS;
typedef pair<int,int> PII;
typedef istringstream ISS;
typedef ostringstream OSS;

#define REP( i, m, n ) for ( int i = (int)( m ); i < (int)( n ); ++i )
#define EACH( v, c ) for ( auto &v : c )

#define ITER( c ) __typeof( (c).begin() )
#define IREP( c, it ) for ( ITER(c) it = c.begin(); it != c.end(); ++it )
#define ALL( c ) (c).begin(), (c).end()

#define PB( n ) push_back( n )
#define MP( a, b ) make_pair( ( a ), ( b ) )
#define EXIST( c, e ) ( (c).find( e ) != (c).end() )

#define fst first
#define snd second

#define DUMP( x ) cerr << #x << " = " << ( x ) << endl
#define DEBUG( x ) cerr << __FILE__ << ":" << __LINE__ << ": " << #x << " = " << ( x ) << endl

const string table[] = {
	"abcde",
	"fghij",
	"klmno",
	"pqrst",
	"uvwxy",
	"z.?! ",
};

string solve( string src )
{
	if ( src.size() % 2 )
	{
		return "NA";
	}

	string res;

	for ( int i = 0; i < src.size(); i += 2 )
	{
		int idx1 = src[i] - '1', idx2 = src[ i + 1 ] - '1';
		if ( 6 <= idx1 || 5 <= idx2 )
		{
			return "NA";
		}
		res += table[ idx1 ][ idx2 ];
	}

	return res;
}

int main()
{
	cin.tie( 0 );
	ios::sync_with_stdio( false );

	string str;
	while ( cin >> str )
	{
		cout << solve( str ) << endl;
	}

	return 0;
}