#include <bits/stdc++.h>
using namespace std;
int a, b, c, Count = 1;
int main() {
  cin >> a >> b >> c;
  if ((a + b > c) && (a + c > b) && (b + c > a)) {
    cout << 0 << endl;
    return 0;
  }
  while ((a + b < c) || (a + c < b) || (b + c < a)) {
    ++Count;
    if (a + b < c) {
      if (a < b)
        a++;
      else
        b++;
    } else if (a + c < b) {
      if (a < c)
        a++;
      else
        c++;
    } else if (b + c < a) {
      if (b < c)
        b++;
      else
        c++;
    }
  }
  cout << Count << endl;
  return 0;
}
