#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;
#define rep(i,n) for(int i=0;i<n;i++)
#define INF (1<<21)

bool chk(char x,char y){
	return x>='1' && x <= '6' && y >= '1' && y <= '5';
}
string table[5] =
{
	"afkpuz",
	"bglqv.",
	"chmrw?",
	"dinsx!",
	"ejoty "
};
char get(char x,char y){
	x -= '1' , y -= '1';
	return table[y][x];
}
int main(){
	string str;
	while(cin >> str){
		bool f = 1;
		if(str.size() % 2) f = 0;
		for(int i=0;i<str.size();i+=2)
			f &= chk(str[i],str[i+1]);
		if(f){
			for(int i=0;i<str.size();i+=2)
				cout << get(str[i],str[i+1]);
			cout << endl;
		}else{
			cout << "NA" << endl;
		}
	}
}