#include <bits/stdc++.h>

using namespace std;

#define FOR(i,a,b) for(int i=(a);i<(b);i++)
#define REP(i,n) FOR(i,0,n)

int main() {
	string str[5] = {"afkpuz","bglqv.","chmrw?","dinsx!","ejoty "};
	string in;
	
	while (cin >> in) {
		string ans = "";
		
		if (in.size() & 1) {
			puts("NA");
			continue;
		}
		REP(i, in.size() / 2) {
			int pos = i * 2;
			int a = in[pos] - '0', b = in[pos + 1] - '0';
			if (!(a >= 1 && a <= 6 && b >= 1 && b <= 5)) {
				ans = "NA";
				break;
			}
			a--; b--;
			ans += str[b][a];
		}
		
		cout << ans << endl;
	}
	return 0;
}