#include "bits/stdc++.h"
using namespace std;
using namespace std;

char table[6][5] = {
	{'a','b','c','d','e'},
	{'f','g','h','i','j'},
	{'k','l','m','n','o'},
	{'p','q','r','s','t'},
	{'u','v','w','x','y'},
	{'z','.','?','!',' '}
};

int main(){
	string s;
	while( cin >> s ){
		string ans;
		if( s.size()%2 ){
			cout << "NA" << endl;
		}else{
			bool flag = false;
			for(int i=1 ; i < s.size() ; i+=2 ){
				int y = s[i-1]-'0'-1;
				int x = s[i]-'0'-1;
				if( y < 0 || x < 0 || y >= 6 || x >= 5 ){
					flag = true;
					break;
				}
				ans += table[y][x];
			}
			if( flag )
				cout << "NA" << endl;
			else
				cout << ans << endl;
		}
	}
}