#include <bits/stdc++.h>
using namespace std;
const string hyou[] = {"afkpuz", "bglqv.", "chmrw?", "dinsx!", "ejoty "};
int main() {
  string in;
  while (cin >> in) {
    cin.ignore();
    if (in.size() % 2 == 1) {
      cout << "NA" << endl;
      continue;
    }
    for (int i = 0; i < in.size() - 1; i += 2) {
      cout << hyou[in[i + 1] - '0' - 1][in[i] - '0' - 1];
    }
    cout << endl;
  }
  return 0;
}
