#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
#include<cassert>
#include<iostream>
#include<sstream>
#include<string>
#include<vector>
#include<queue>
#include<set>
#include<map>
#include<utility>
#include<numeric>
#include<algorithm>
#include<bitset>
#include<complex>

using namespace std;

typedef long long Int;
typedef vector<int> vint;
typedef pair<int,int> pint;
#define mp make_pair

template<class T> void pv(T a, T b) { for (T i = a; i != b; ++i) cout << *i << " "; cout << endl; }
template<class T> void chmin(T &t, T f) { if (t > f) t = f; }
template<class T> void chmax(T &t, T f) { if (t < f) t = f; }
int in() { int x; scanf("%d", &x); return x; }

int main() {
	string str;
	while(getline(cin,str)){
		string res="";
		int i;
		if(str.size()%2>0){
			cout<<"NA"<<endl;
			continue;
		}
		for(i=0;i<str.size();i+=2){
			if(str[i]<'1'||'6'<str[i]||str[i+1]<'1'||'5'<str[i+1]){
				cout<<"NA"<<endl;
				goto a;
			}
			if(str[i]!='6'){
				res+='a'+(str[i]-'1')*5+str[i+1]-'1';
			}else{
				switch(str[i+1]){
				case '1':
					res+="z";
					break;
				case '2':
					res+=".";
					break;
				case '3':
					res+="?";
					break;
				case '4':
					res+="!";
					break;
				case '5':
					res+=" ";
					break;
				}
			}
		}
		cout<<res<<endl;
		a:;
	}
	return 0;
}