Problem:
Score : 200 points

Problem Statement

AtCoDeer the deer found two rectangles lying on the table, each with height 1 and width W.
If we consider the surface of the desk as a two-dimensional plane, the first rectangle covers the vertical range of [0,1] and the horizontal range of [a,a+W], and the second rectangle covers the vertical range of [1,2] and the horizontal range of [b,b+W], as shown in the following figure:

AtCoDeer will move the second rectangle horizontally so that it connects with the first rectangle.
Find the minimum distance it needs to be moved.

Constraints

All input values are integers.

1≤W≤10^5

1≤a,b≤10^5

Input

The input is given from Standard Input in the following format:

W a b

Output

Print the minimum distance the second rectangle needs to be moved.

Sample Input 1

3 2 6

Sample Output 1

1

This input corresponds to the figure in the statement. In this case, the second rectangle should be moved to the left by a distance of 1.

Sample Input 2

3 1 3

Sample Output 2

0

The rectangles are already connected, and thus no move is needed.

Sample Input 3

5 10 1

Sample Output 3

4

Solution in C++14 (GCC 5.4.1) (judge verdict: Accepted)

#include <bits/stdc++.h>
using namespace std;

const double pi  = 2 * acos(0.0);
const double eps = 1e-8;

#define REP(i,a,b) for(int i=(a); i<(b);++i)
#define rep(i,n) REP(i,0,n)
#define INF (1<<29)
#define INFLL (1LL<<61)

typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;

typedef int Cost;
struct Edge {
  int src, dst; Cost cost;
  Edge(int s, int d, Cost c) : src(s), dst(d), cost(c) {}
};
typedef vector<Edge>  Edges;
typedef vector<Edges> Graph;
typedef vector<Cost>  Array;
typedef vector<Array> Matrix;

int dx[8] = {0, 1, 0, -1, 1, -1, 1, -1};
int dy[8] = {1, 0, -1, 0, 1, -1, -1, 1};

int main(void) {
  ios_base::sync_with_stdio(false); cin.tie(0);
  int W, a, b;
  cin >> W >> a >> b;

  if ((a <= b && b <= a + W) || (b <= a && a <= b + W)) {
    cout << 0 << endl;
    return 0;
  }

  int d1 = abs(b-a-W);
  int d2 = abs(a-b-W);

  if (d1 > d2) cout << d2 << endl;
  else cout << d1 << endl;
}