#include<iostream>
#include<string>
using namespace std;
int main(){
  string nums,text,ch;
  ch = "abcdefghijklmnopqrstuvwxyz.?! ";
  while(cin>>nums){
    text = "";
    if(nums.size()%2){
      cout<<"NA"<<endl;
    }
    else{
      for(int i=0;i<nums.size()/2;i++){
	if('0'<nums[i*2]&&nums[i*2]<'7'&&'0'<nums[i*2+1]&&nums[i*2+1]<'6')
	  text=text+ch[5*(nums[i*2]-49)+(nums[i*2+1]-49)];
	else{
	  text="NA";
	  break;
	}
      }
      cout<<text<<endl;
    }
  }
  return 0;
}