How can a Win32 process get the pid of its parent?

#include <stdio.h>
#include <windows.h>
#include <tlhelp32.h>

int main(int argc, char *argv[])
{
    int pid = -1;
    HANDLE h = CreateToolhelp32Snapshot(TH32CS_SNAPPROCESS, 0);
    PROCESSENTRY32 pe = { 0 };
    pe.dwSize = sizeof(PROCESSENTRY32);

    //assume first arg is the PID to get the PPID for, or use own PID
    if (argc > 1) {
    	pid = atoi(argv[1]);
    } else {
    	pid = GetCurrentProcessId();
    }

    if( Process32First(h, &pe)) {
    	do {
    		if (pe.th32ProcessID == pid) {
    			printf("PID: %i; PPID: %in", pid, pe.th32ParentProcessID);
    		}
    	} while( Process32Next(h, &pe));
    }

    CloseHandle(h);
}

ULONG_PTR GetParentProcessId() // By Napalm @ NetCore2K
{
 ULONG_PTR pbi[6];
 ULONG ulSize = 0;
 LONG (WINAPI *NtQueryInformationProcess)(HANDLE ProcessHandle, ULONG ProcessInformationClass,
  PVOID ProcessInformation, ULONG ProcessInformationLength, PULONG ReturnLength);
 *(FARPROC *)&NtQueryInformationProcess =
  GetProcAddress(LoadLibraryA("NTDLL.DLL"), "NtQueryInformationProcess");
 if(NtQueryInformationProcess){
  if(NtQueryInformationProcess(GetCurrentProcess(), 0,
    &pbi, sizeof(pbi), &ulSize) >= 0 && ulSize == sizeof(pbi))
     return pbi[5];
 }
 return (ULONG_PTR)-1;
}