Calculate vowels with Cpp

#include <iostream>
#include <cstdlib>

using std::cerr;
using std::cout;
using std::endl;

int main(int argc, char *argv[]) {
  if (argc < 2) {
    cerr << "Usage: " << argv[0] << " word01 word02 word03 ..." << endl;
    exit(EXIT_FAILURE);
  }

  unsigned count = 0;
  for (unsigned i = 1; i < argc; i++) {
    // loop by pointer
    for (char *p = argv[i]; *p != '\0'; p++) {
      switch (*p) {
      case 'a':
      case 'A':
      case 'e':
      case 'E':
      case 'i':
      case 'I':
      case 'o':
      case 'O':
      case 'u':
      case 'U':
    count++;
    break;
      }
    }
  }

  cout << count << endl;
  return 0;
}