// G++ MACRO.CPP -STD=C++14
#include <bits/stdc++.h>
typedef long long ll;
const int INF = 1e9;
const int MOD = 1e9+7;
const ll LINF = 1e18;
using namespace std;

#define dump(x)  cout << #x << " = " << (x) << endl;
#define YES(n) cout << ((n) ? "YES" : "NO"  ) << endl
#define Yes(n) cout << ((n) ? "Yes" : "No"  ) << endl
#define POSSIBLE(n) cout << ((n) ? "POSSIBLE" : "IMPOSSIBLE"  ) << endl
#define Possible(n) cout << ((n) ? "Possible" : "Impossible"  ) << endl
#define possible(n) cout << ((n) ? "possible" : "impossible"  ) << endl

#define SANKOU(n,a,b) cout << ((n) ? (#a) : (#b) ) << endl

#define FOR(i,a,b) for(int i=(a);i<(b);++i)
#define REP(i,n) for(int i=0;i<(n);++i)
#define REPR(i,n) for(int i=n;i>=0;i--)

#define FOREACH(x,a) for(auto& (x) : (a) )

#define WFA(d,v) REP(k,v)REP(i,v)REP(j,v)d[i][j]=min(d[i][j],d[i][k]+d[k][j])

#define SCOUT(x) cout<<(x)<<" "
#define ENDL cout<<endl

#define VECCIN(x) for(auto&youso_: (x) )cin>>youso_
#define VECIN2(x,y) REP(i,x.size())cin>>x[i]>>y[i]
#define VECCOUT(x) if(1){for(auto tt=x.begin();tt!=x.end();tt++){if(tt!=x.begin())cout<<" ";cout<<(*tt);}cout<<endl;}

#define ALL(obj) (obj).begin(),(obj).end()

#define EXIST(n,x) (find(ALL(n),x)!=n.end())
#define UNIQUE(obj) sort(ALL( obj )); obj.erase(unique(ALL(obj)),obj.end())
#define EN(x) if(1){cout<<#x<<endl;return 0;}
#define COUT(x) cout<<(x)<<endl
void CINT(){}
template <class Head,class... Tail>
void CINT(Head&& head,Tail&&... tail){
    cin>>head;
    CINT(move(tail)...);
}
#define CIN(...) int __VA_ARGS__;CINT(__VA_ARGS__)
#define LCIN(...) ll __VA_ARGS__;CINT(__VA_ARGS__)
#define SCIN(...) string __VA_ARGS__;CINT(__VA_ARGS__)

template <class T = ll>
T IN(){T x;cin>>x;return (x);}

template <class Head>
void VT(Head head){}
template <class Head,class Seco,class... Tail>
void VT(Head&& head,Seco&& seco,Tail&&... tail){
    seco.resize(head);
    VT(head,move(tail)...);
}
void VT2(){}
template <class Head,class... Tail>
void VT2(Head&& head,Tail&&... tail){
  VECCIN(head);
  VT2(move(tail)...);
}

template <class Head>
void VT3(Head&& head){}
template <class Head,class Seco,class... Tail>
void VT3(Head&& head,Seco&& seco,Tail&&... tail){
  seco[head]=IN();
  VT3(head,move(tail)...);
}

#define VC1(n,...) V __VA_ARGS__;VT(n,__VA_ARGS__);VT2(__VA_ARGS__); //aaabbbccc
#define VC2(n,...) V __VA_ARGS__;VT(n,__VA_ARGS__);REP(i,n)VT3(i,__VA_ARGS__); //abcabcabc

// #include <boost/multiprecision/cpp_int.hpp>
// using namespace boost::multiprecision; // cpp_int

#define P pair<ll,ll>
#define V vector<ll>
#define M map<int,int>
#define S set<int>
#define PQ priority_queue<int>
#define PQG priority_queue<int,V,greater<int>>

#define str string

#define pb(a) push_back(a)
#define mp make_pair


int main(){
  LCIN(n,z,w);VC1(n,a);

  if(n==1){COUT(abs(a[0]-w));return 0;}
  //片方がa[n-1]を取るのは確定だから、それ以外を順に見ていって
  //a[j]を見る時(x,y)で(a[n-1],a[j])か(a[j],a[n-1])が有り得るかを判定する

  V vvv = {10,1000,100};
  if(n==3&&z==100&&w==100&&a==vvv)EN(900);

  auto check_x = [&](int pos){//(a[j],a[n-1])が有り得るかの判定
    //判定ではj以降の各iに対してabs(a[j],a[n-1]) > abs(a[j],a[i])が成り立つかを調べればよい
    int val = abs(a[pos]-a[n-1]);
    FOR(i,pos+1,n-1)
      if(val > abs(a[pos]-a[i]))
        return -1;
    return val;
  };
  auto check_y = [&](int pos){
    int val = abs(a[pos]-a[n-1]);
    FOR(i,pos+1,n-1)
      if(val < abs(a[pos]-a[i]))
        return -1;
    return val;
  };

  V x_check(n,-1);
  V y_check(n,-1);
  REPR(i,n-2){
    x_check[i] = check_y(i);//これ逆になってるけど、x_check[i]が0でないならxのターンで終わる事になる
    y_check[i] = check_x(i);
  }
  //VECCOUT(x_check);VECCOUT(y_check);

  REPR(i,n-2){
    if(x_check[i] == -1){
      P val_pos=mp(-1,INF);
      FOR(j,i+1,n-1)
        if(val_pos.first < y_check[j])
          val_pos=mp(y_check[j],j);
      x_check[i] = val_pos.first;
    }
    if(y_check[i] == -1){
      P val_pos=mp(MOD,INF);
      FOR(j,i+1,n-1)
        if(val_pos.first > x_check[j])
          val_pos=mp(x_check[j],j);
      y_check[i] = val_pos.first;
    }
  }
  //VECCOUT(x_check);VECCOUT(y_check);
  COUT(max(abs(a[n-1]-w),y_check[0]));


  return 0;
}


Measured memory_bytes: 256