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

int main(){
    char field[6][11];
    char a='a';
    for(int i=1; i < 7; i++){
        for(int j=1; j < 6; j++){
            field[j][i] = a;
            a++;
        }
    }
    field[2][6] = '.'; field[3][6] = '?'; field[4][6] = '!'; field[5][6] = ' ';

    string input;
    while(cin >> input){
        string ans;
        bool isCorrect = true;
        if(input.size()%2 == 1) {
            isCorrect = false;
        }
        else {
            for(int i=0; i < input.size(); i+=2){
                int n = atoi(input.substr(i, 1).c_str());
                int m = atoi(input.substr(i+1, 1).c_str());
                if(!(1 <= m && m <= 5 && 1 <= n && n <= 6)) isCorrect = false;
                ans += field[m][n];
            }
        }
        if(isCorrect) cout << ans << endl;
        else cout << "NA" << endl;
    }
}