#include <bits/stdc++.h>
char str[5][7] = {{"afkpuz"}, {"bglqv."}, {"chmrw?"}, {"dinsx!"}, {"ejoty "}};
int main() {
  char n[500] = "";
  int i;
  for (; ~fscanf(stdin, "%[^\n]*s", n); memset(n, '\0', sizeof(n)), puts("")) {
    getchar();
    if (strlen(n) & 1) {
      fprintf(stdout, "NA");
      ;
      continue;
    }
    for (i = 0; i < strlen(n); i += 2)
      fprintf(stdout, "%c", str[(n[i + 1] - '0') - 1][(n[i] - '0') - 1]);
  }
  return 0;
}
