#include <bits/stdc++.h>
#pragma warning(disable : 4996)
char c[201], d[101];
int main() {
  while (~scanf("%s", c)) {
    if (strlen(c) % 2 == 1) {
      printf("NA\n");
    } else {
      bool flag = false;
      for (int i = 0; i < strlen(c); i += 2) {
        int a = c[i] - 48, b = c[i + 1] - 48;
        if (a == 0 || a > 6 || b == 0 || b > 5) {
          printf("NA");
          flag = true;
          break;
        } else {
          int e = (a - 1) * 5 + (b - 1);
          switch (e) {
            case 26:
              d[i / 2] = '.';
              break;
            case 27:
              d[i / 2] - '?';
              break;
            case 28:
              d[i / 2] = '!';
              break;
            case 29:
              d[i / 2] = ' ';
              break;
            default:
              d[i / 2] = (char)(e + 97);
          }
        }
      }
      if (!flag) {
        for (int i = 0; i < strlen(c) / 2; i++) {
          printf("%c", d[i]);
        }
      }
      printf("\n");
    }
  }
  return 0;
}
