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

char table[6][5] = {
  {'a','b','c','d','e'},
  {'f','g','h','i','j'},
  {'k','l','m','n','o'},
  {'p','q','r','s','t'},
  {'u','v','w','x','y'},
  {'z','.','?','!',' '}
};

int main(){
  string s;
  while( cin >> s ){
    string ans;
    if( s.size() % 2 ){
      cout << "NA" << endl;
    }else{
      bool flag = false;
      for(int i=1 ; i < s.size() ; i+=2 ){
	int y = s[i-1]-'0'-1;
	int x = s[i]-'0'-1;
	if( y < 0 || x < 0 || y >= 6 || x >= 5 ){
	  flag = true;
	  break;
	}
	ans += table[y][x];
      }
      if( flag )
	cout << "NA" << endl;
      else
	cout << ans << endl;
    }
  }
}