fscanf parse data (format specifier) C++

I have a struct like so:

struct Office {
char city[50];
int employees;
char desc[200];
}

struct Office office[100];

Then I want to fill the office array within a loop until reach end of file.

here is my data:

Toronto
    151: This is HQ

Vancouver
    23: This is branch office

London
    12: This is euro branch

Take this as an example:

Toronto
    151: This is HQ

So here I want to parse it to struct:

city = "Toronto"
employees = 151
desc = "This is HQ"

Notice: After city name in the new line before the number of employess, there is TAB (4 spaces)

I have had an implementation like so, but seems it does not work properly:

int function LoadOffices(const char *f) {
  int res = 1;
  char buf[500];
  char city[50];
  int emp;
  char desc[200];
  struct Office offices[100];
  FILE *fp = fopen(f, "r");

  if (fp) {
    while (fgets(buf, sizeof(line), fp) != nullptr) {
      if (i == 0) {
        rewind(fp);
      }
      i++;
      if (fscanf(fp, "%[^\n]", city) == 1) {
        strncpy(offices[i].city, city, 50);
      } else if (fscanf(fp, "%d[^:]:%[^\n]", &emp, desc) == 2) {
        offices[i].employees = emp;
        strncpy(offices[i].desc, desc, 200);
      }
    }
    res = 0;
  } else {
    res = 1;
  }

  fclose(fp);
  return res;
}

I just want to know how to deal with TAB and empty lines