#include<iostream>
#include<string>
using namespace std;
int main()
{
	string s,r;
	int i;
	const char *a[7] = 
	{
		"afkpuz",
		"bglqv.",
		"chmrw?",
		"dinsx!",
		"ejoty ",
	};
	while(cin >> s)
	{
		r="";
		for(i=0;i+1<s.size();i+=2)
		{
			if(s[i]>'6' || s[i+1]>'5') break; 
			r+=a[s[i+1]-'1'][s[i]-'1'];
		}
		if(i != s.size())
			cout << "NA"<<endl;
		else
			cout << r << endl;
	}
	return 0;
}