#include <bits/stdc++.h>
int look(long long h) {
  long long j, m = 1;
  for (j = 2; j <= sqrt(h); j++) {
    if (h % j == 0) {
      m = 0;
      break;
    }
  }
  return m;
}
int main() {
  long long a, num;
  long long i, j, m;
  while (~scanf("%lld", &a) && a) {
    if (look(a))
      printf("1\n");
    else if (a % 2 == 0)
      printf("%lld\n", a / 2);
    else {
      for (i = 2; i <= a; i++) {
        m = 0;
        if (a % i == 0) {
          m = look(i);
          if (m) {
            printf("%lld\n", 1 + (a - i) / 2);
          }
        }
        if (m == 1) break;
      }
    }
  }
  return 0;
}
