#include<iostream>
#include<string>
using namespace std;
int main(void){
	const char *table[] ={
		"afkpuz",
		"bglqv.",
		"chmrw?",
		"dinsx!",
		"ejoty "
	};

	while( true ){
		bool bNA = false;
		string s;

		cin >> s;

		if( cin.eof() )
			break;

		if( s.length() % 2 == 1 ){
			bNA = true;
			goto NA;
		}
		for(unsigned int l = 0; l < s.length(); l += 2){
			int i = s[l+1]-'0'-1;
			int j = s[l]-'0'-1;
			if( !(0 <= i && i <= 4) || !(0 <= j && j <= 5) ){
				bNA = true;
				goto NA;
			}
		}
NA:;
		if( bNA ){
			cout << "NA\n";
			continue;
		}

		for(unsigned int l = 0; l < s.length(); l += 2){
			int i = s[l+1]-'0'-1;
			int j = s[l]-'0'-1;
			cout << table[i][j];
		}
		cout << '\n';
	}

	return 0;
}