#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <queue>
#include <stack>
#include <vector>
#include <algorithm>
#include <string>
#include <cstring>
#include <cmath>
#include <complex>
#include <map>
#include <climits>
#include <sstream>
using namespace std;

#define reep(i,a,b) for(int i=(a);i<(b);++i)
#define rep(i,n) reep((i),0,(n))
#define ALL(v) (v).begin(),(v).end()
#define PB push_back
#define EPS 1e-8
#define F first
#define S second
#define mkp make_pair

static const double PI=6*asin(0.5);
typedef long long ll;
typedef complex<double> CP;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;
typedef vector<int> vint;
static const int INF=1<<24;

template <class T>
void initvv(vector<vector<T> > &v,int a,int b, const T  &t = T()){
	v.assign(a,vector<T>(b,t));
}

//v.erase(unique(v.begin(),v.end()),v.end());

string a[]={"abcde","fghij","klmno","pqrst","uvwxy","z.?! "};

int main(){
	string s;
	while(cin>>s){
		stringstream ss;
		if(s.size()%2){
			cout<<"NA\n";
			continue;
		}
		bool f=false;
		rep(i,s.size()){
			int x=s[i]-'0'-1,y=s[i+1]-'0'-1;
			if(!(-1<x&&x<6)||!(-1<y&&y<5)){
				// cout<<x<<" "<<y<<endl;
				f=true;
				break;
			}
			ss<<a[x][y];
			i++;
		}
		if(f){
			cout<<"NA\n";
			continue;
		}
		string tmp;
		getline(ss,tmp);
		cout<<tmp<<endl;
	}
}