#include<iostream>
#include<string>
using namespace std;

int main(){

  string s[5] = {"afkpuz","bglqv.","chmrw?","dinsx!","ejoty "};
  string t;
  int z,x,y;

  while(cin >> t){
    z = 0;

    if(t.size()%2 == 1){
      cout << "NA" << endl;
      continue;
    }

    for(int i=0;i<t.size();i++){
      if(i%2 == 0){
	if(t[i] < '1' || t[i] > '6'){
	  cout << "NA" << endl;
	  z = 1;
	  break;
	}
      }

      if(i%2 == 1){
	if(t[i] < '1' || t[i] > '5'){
	  cout << "NA" << endl;
	  z = 1;
	  break;
	}
      }
    }

    if(z == 1) continue;

    for(int i=0;i<t.size();i+=2){
      x = t[i] -'0'-1;
      y = t[i+1] - '0'-1;

      cout << s[y][x];
    }

    cout << endl;
  }
}