#include <bits/stdc++.h>
int main() {
  const int LIMIT = 100;
  int numSticks;
  scanf("%d", &numSticks);
  int array[LIMIT + 1] = {0};
  int temp(0), total(0);
  for (int k = 0; k < numSticks; k++) {
    scanf("%d", &temp);
    ++array[temp];
  }
  for (int k = 0; k <= LIMIT; k++) {
    total += array[k] / 2;
  }
  total /= 2;
  printf("%d\n", total);
  return 0;
}
