
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cmath>
#include <ctime>
#include <cassert>
#include <iostream>
#include <cctype>
#include <sstream>
#include <string>
#include <list>
#include <vector>
#include <queue>
#include <set>
#include <stack>
#include <map>
#include <utility>
#include <numeric>
#include <algorithm>
#include <iterator>
#include <bitset>
#include <complex>
#include <fstream>
using namespace std;
typedef long long ll;
const double EPS = 1e-9;
typedef vector<int> vint;
typedef pair<int, int> pint;
#define rep(i, n) REP(i, 0, n)
#define ALL(v) v.begin(), v.end()
#define MSG(a) cout << #a << " " << a << endl;
#define REP(i, x, n) for(int i = x; i < n; i++)
template<class T> T RoundOff(T a){ return int(a+.5-(a<0)); }
template<class T, class C> void chmax(T& a, C b){ if(a < b) a = b; }
template<class T, class C> void chmin(T& a, C b){ if(b < a) a = b; }
template<class T, class C> pair<T, C> mp(T a, C b){ return make_pair(a, b); }

int main()
{
    string table[6] = {	"abcde", "fghij", "klmno", "pqrst", "uvwxy", "z.?! "	};
	
	for(string line; cin >> line;)
	{
		if(line.size() % 2)
		{
			cout << "NA" << endl;
			continue;
		}
		
		string ans;
		rep(i, line.size() / 2) if('1' <= line[i * 2] && line[i * 2] <= '6' && '1' <= line[i * 2 + 1] && line[i * 2 + 1] <= '5')
			ans += table[line[i * 2] - '1'][line[i * 2 + 1] - '1'];
		
		if(ans.size() * 2 == line.size())
			cout << ans << endl;
		else
			cout << "NA" << endl;
	}
}