#include <bits/stdc++.h>
#define rep(i,n)for(long long i=0;i<(long long)(n);++i)
#define all(a) a.begin(), a.end()
using namespace std;
typedef long long ll;
typedef pair<ll, ll> P;
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return true; } return false; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return true; } return false; }
 
const ll MOD=1e9+7;
const ll INF=1e18;
const int MAX=510000;
const double pi=acos(-1);
int dx[8] = {1,0,-1,0,1,1,-1,-1};
int dy[8] = {0,1,0,-1,-1,1,1,-1};

int main(){
  cin.tie(0);
  ios::sync_with_stdio(false); 
  
  int a,b,c;
  cin >> a >> b >> c;
  ll ans = min({abs(a-b),abs(b-c),abs(c-a)});
  int na=a,nb=b,nc=c;
  ll sum=0;
  if(b<=a){
    nb=a+1;
    sum+=nb-b;
  }
  if(c<=nb){
    nc=nb+1;
    sum+=nc-c;
  }
  ans=min(ans,sum);
  
  sum=0;
  nb=b;
  nc=c;
  if(b<=c){
    nb=c+1;
    sum+=nb-b;
  }
  if(a<=nb){
    na=nb+1;
    sum+=na-a;
  }
  ans=min(ans,sum);
  
  cout << ans << endl;
  
  return 0;
}