#include<bits/stdc++.h>
#define rep(i,n)for(int i=0;i<n;i++)
using namespace std;

int main() {
	string s;
	while (cin >> s) {
		if (s.size() % 2) { puts("NA"); continue; }
		string res;
		int pos = 0;
		while (pos + 1 < s.size()) {
			int d = stoi(to_string(s[pos] - 48) + to_string(s[pos + 1] - 48));
			if (d <= 10 || 65 < d) { puts("NA"); goto p; }
			if (d <= 15)res += (char)d + 86;
			else if (d <= 25)res += (char)d + 81;
			else if (d <= 35)res += (char)d + 76;
			else if (d <= 45)res += (char)d + 71;
			else if (d <= 55)res += (char)d + 66;
			if (d == 61)res += 'z';
			if (d == 62)res += '.';
			if (d == 63)res += '?';
			if (d == 64)res += '!';
			if (d == 65)res += ' ';
			pos += 2;
		}
		cout << res << endl;
	p:;
	}
}