#include<iostream>
#include<algorithm>
#include<cstdio>
#include<cmath>
#include<math.h>
#include<string>
#include<string.h>
#include<stack>
#include<queue>
#include<vector>
#include<utility>
#include<set>
#include<map>
#include<stdlib.h>
#include<iomanip>
  
using namespace std;
  
#define ll long long
#define ld long double
#define EPS 0.0000000001
#define INF 1e9
#define MOD 1000000007
#define rep(i,n) for(i=0;i<n;i++)
#define loop(i,a,n) for(i=a;i<n;i++)
#define all(in) in.begin(),in.end()
#define shosu(x) fixed<<setprecision(x)
  
typedef vector<int> vi;
typedef pair<int,int> pii;
  
int main(void) {
  int i,j;
  string s;
  char a[6][6]={"abcde","fghij","klmno","pqrst","uvwxy","z.?! "};
  while(cin>>s){
    string ans="";
    if(s.size()%2){
      cout<<"NA"<<endl;
      continue;
    }
    rep(i,s.size()){
      if(s[i]<'1' || s[i]>'6' || s[i+1]<'1' || s[i+1]>'5'){
    ans="NA";
    break;
      }
      ans+=a[s[i]-'0'-1][s[i+1]-'0'-1];
      i++;
    }
    cout<<ans<<endl;
  }
}