#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  scanf("%d", &n);
  if (n < 0) n = -n;
  int up = int(sqrt(2 * n + 100000)) + 1000;
  for (int k = 0; k <= up; k++) {
    long long m = n + k * (long long)(k + 1) / 2;
    if (m & 1) continue;
    if (k * (long long)(k + 1) >= m) return 0 * printf("%d\n", k);
  }
  printf(":(\n");
  return 0;
}
