#include <bits/stdc++.h>
using namespace std;
int main() {
  long long arr[3];
  cin >> arr[0] >> arr[1] >> arr[2];
  sort(arr, arr + 3);
  if (arr[2] > arr[1]) {
    arr[1]++;
  }
  if (arr[2] > arr[0]) {
    arr[0]++;
  }
  cout << 2 * arr[2] - arr[0] - arr[1] << endl;
}
