#include<iostream>
using namespace std;

int main()
{
  string s;

  for(;cin>>s;)
    {
      bool flag=true;
      string ans="";
      if(s.size()%2!=0)
	  flag=false;
      for(int i=0;i<s.size()&&flag;i+=2)
	{
	  if(s[i]>'6' ||s[i+1]>'5'||s[i]<'1'||s[i+1]<'1')
	    flag=false;

	  if(s[i]=='6')
	    {
	      if(s[i+1]=='1')
		ans+="z";
	      if(s[i+1]=='2')
		ans+=".";
	      if(s[i+1]=='3')
		ans+="?";
	      if(s[i+1]=='4')
		ans+="!";
	      if(s[i+1]=='5')
		ans+=" ";
	    }
	  else
	    {
	      int a=s[i]-'0';
	      int b=s[i+1]-'0';
	      char tmp='a'+(5*(a-1))+(b-1);
	      ans+=tmp;
	    }
	}
      
      if(flag)
	cout<<ans<<endl;
      else
	cout<<"NA"<<endl;
    }
}