#include <bits/stdc++.h>
using namespace std;
int main() {
  char l[6][6] = {{0}};
  for (int i = 0; i < 5; i++) {
    for (int j = 0; j < 5; j++) l[i][j] = 'a' + i * 5 + j;
  }
  strcpy(l[5], "z.?! ");
  char str[256];
  while (scanf("%s", str) != EOF) {
    if (strlen(str) & 1) {
      puts("NA");
      continue;
    }
    char ans[128] = {0};
    for (int i = 0; str[i]; i += 2) {
      int v1 = str[i] - '0' - 1, v2 = str[i + 1] - '0' - 1;
      if (v1 < 0 || v1 >= 6 || v2 < 0 || v2 >= 5) {
        puts("NA");
        break;
      }
      ans[i / 2] = l[v1][v2];
    }
    printf("%s\n", ans);
  }
  return 0;
}
