#include<iostream>
#include<string>
using namespace std;

string mp[6] = {"abcde", "fghij", "klmno", "pqrst", "uvwxy", "z.?! " };

int main() {
    string s;
    while(cin>>s) {
        if(s.length()%2) {
            cout<<"NA"<<endl;
            continue;
        }

        string res = "";
        for(int i=0; i<s.length(); i+=2) {
            if(s[i] >= '7' || s[i] <= '0' || s[i+1] >= '6' || s[i+1] <= '0') {
                cout<<"NA"<<endl;
                goto NEXT;
            }
            res += string(1, mp[s[i]-'1'][s[i+1]-'1']);
        }

        cout<<res<<endl;
    NEXT:;
    }
}