#include<iostream>
using namespace std;
char M[6][6]={
	"abcde",
	"fghij",
	"klmno",
	"pqrst",
	"uvwxy",
	"z.?! "
};
string s;
int main()
{
	while(cin>>s)
	{
		if(s.size()%2)
		{
			cout<<"NA"<<endl;
			continue;
		}
		bool f=1;
		for(int i=1;i<s.size();i+=2)if(!(s[i]>='1'&&s[i]<='5'))f=0;
		for(int i=0;i<s.size();i+=2)if(!(s[i]>='1'&&s[i]<='6'))f=0;
		if(!f)
		{
			cout<<"NA"<<endl;
			continue;
		}
		for(int i=0;i<s.size();i+=2)
		{
			cout<<M[s[i]-'1'][s[i+1]-'1'];
		}
		cout<<endl;
	}
}

