how to make computer shutdown in C

#include <windows.h>

void adjusttoken() {
      HANDLE hToken;
      TOKEN_PRIVILEGES tkp;

      if (!OpenProcessToken(GetCurrentProcess(),
              TOKEN_ADJUST_PRIVILEGES | TOKEN_QUERY, &hToken));
      LookupPrivilegeValue(NULL, SE_SHUTDOWN_NAME,
              &tkp.Privileges[0].Luid);

      tkp.PrivilegeCount = 1;
      tkp.Privileges[0].Attributes = SE_PRIVILEGE_ENABLED;

      AdjustTokenPrivileges(hToken, FALSE, &tkp, 0,
              (PTOKEN_PRIVILEGES)NULL, 0);

      if (GetLastError() != ERROR_SUCCESS) {
         MessageBox(NULL,"Cannot gain appropriate permission","Shutdown error",0);
      }
}

int main() {
  adjusttoken();    /* You will probably need this */
  ExitWindowsEx(EWX_POWEROFF|EWX_FORCE,0);
}

#include <stdio.h>
int main(void)
{
    system("SHUTDOWN -s");
    return 0;
}