#include <bits/stdc++.h>
using namespace std;
int main() {
  char change[6][6] = {"abcde", "fghij", "klmno", "pqrst", "uvwxy", "z.?! "};
  char str[256];
  while (scanf("%s", str) != EOF) {
    char str2[256];
    strcpy(str2, "");
    int i = 0;
    while (str[i] != '\0') {
      if ((str[i] < '1' || str[i] > '6') ||
          (str[i + 1] < '1' || str[i + 1] > '5')) {
        strcpy(str2, "NA");
        break;
      }
      strncat(str2, &change[str[i] - '0' - 1][str[i + 1] - '0' - 1], 1);
      i += 2;
    }
    printf("%s\n", str2);
  }
  return 0;
}
