#include <iostream>
using namespace std;

int main(){
	char p[5][6] =
	{{'a','f','k','p','u','z'},
	 {'b','g','l','q','v','.'},
	 {'c','h','m','r','w','?'},
	 {'d','i','n','s','x','!'},
	 {'e','j','o','t','y',' '}};
	string s;	
	while(cin >> s){
		bool flag = false;
		for(size_t i=0;i<s.size();i+=2){
			if(s[i]>'6' || s[i]<'1' || s[i+1]>'5' || s[i+1]<'1')
				flag = true;
		}
		if(flag||s.size()%2){
			cout << "NA" << endl;
		}else{
			for(size_t i=0;i<s.size();i+=2){
				cout << p[s[i+1]-'0'-1][s[i]-'0'-1];
			}
			cout << endl;
		}
	}
}