#include<iostream>
#include<string.h>
#include<cstdio>

using namespace std;

int main()
{
  char str[250];
  int i;
  char moji[5][6]={{'a','f','k','p','u','z'},
                   {'b','g','l','q','v','.'},
                   {'c','h','m','r','w','?'},
                   {'d','i','n','s','x','!'},
                   {'e','j','o','t','y',' '}};
  while(scanf("%s",str)!=EOF){
    if(strlen(str)%2){
      cout<<"NA"<<endl;
      continue;
    }
    for(i=0;i<strlen(str);i++)
      cout<<moji[str[2*i+1]-'0'-1][str[2*i]-'0'-1];
    cout<<endl;

  }
}