#include <iostream>
#include <string>

using namespace std;

int main(void){
  string str;

  while(cin >> str){
	int n=str.size();
	int tmpi;
	char tmpc;

	if(n%2==1){
	  cout << "NA" << endl;
	  continue;
	}
	for(int i=0;i<n/2;i++){
	  tmpi = 0;
	  tmpc = str[i*2];
	  tmpi += (tmpc - '0') * 10;
	  tmpc = str[i*2+1];
	  tmpi += tmpc - '0';
	  switch(tmpi){
	  case 11:
		cout << "a";
		break;
	  case 12:
		cout << "b";
		break;
	  case 13:
		cout << "c";
		break;
	  case 14:
		cout << "d";
		break;
	  case 15:
		cout << "e";
		break;
	  case 21:
		cout << "f";
		break;
	  case 22:
		cout << "g";
		break;
	  case 23:
		cout << "h";
		break;
	  case 24:
		cout << "i";
		break;
	  case 25:
		cout << "j";
		break;
	  case 31:
		cout << "k";
		break;
	  case 32:
		cout << "l";
		break;
	  case 33:
		cout << "m";
		break;
	  case 34:
		cout << "n";
		break;
	  case 35:
		cout << "o";
		break;
	  case 41:
		cout << "p";
		break;
	  case 42:
		cout << "q";
		break;
	  case 43:
		cout << "r";
		break;
	  case 44:
		cout << "s";
		break;
	  case 45:
		cout << "t";
		break;
	  case 51:
		cout << "u";
		break;
	  case 52:
		cout << "v";
		break;
	  case 53:
		cout << "w";
		break;
	  case 54:
		cout << "x";
		break;
	  case 55:
		cout << "y";
		break;
	  case 61:
		cout << "z";
		break;
	  case 62:
		cout << ".";
		break;
	  case 63:
		cout << "?";
		break;
	  case 64:
		cout << "!";
		break;
	  case 65:
		cout << " ";
		break;
	  }
	}
	cout << endl;
  }
}