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

string hyou[] = {"afkpuz",
		 "bglqv.",
		 "chmrw?",
		 "dinsx!",
		 "ejoty "};
int main(){
  string in;
  while(cin >> in){
    if(in.size()%2 == 1){
      cout << "NA" << endl;
      continue;
    }
        for(int i = 0 ; i < in.size() ; i+=2 ){
	  cout << hyou[in[i+1]-'0'-1][in[i]-'0'-1];
    }
	cout << endl;
  }
  return 0;
}