#include <iostream>
using namespace std;
int main(){
	char graph[6][7] = {{0,  0,  0,  0,  0,  0,  0},
											{0, 97,102,107,112,117,122},
											{0, 98,103,108,113,118,'.'},
											{0, 99,104,109,114,119,'?'},
											{0,100,105,110,115,120,'!'},
											{0,101,106,111,116,121,' '}};
	string s;
	while(cin >> s,!cin.eof()){
		if(s.size() % 2 == 1){cout << "NA" << endl;continue;};
		for(int i = 0;i < s.size();i += 2){
			if(s[i] - '0' == 0 || s[i+1] - '0' == 0 || s[i] - '0' > 6 || s[i+1] - '0' > 5){cout << "NA";break;}
			cout << graph[s[i+1]-'0'][s[i]-'0'];
		}
		cout << endl;
	}	
}