// need
    #include <iostream>
    #include <algorithm>
     
    // data structure
    #include <bitset>
    #include <map>
    #include <queue>
    #include <set>
    #include <stack>
    #include <string>
    #include <utility>
    #include <vector>
    //#include <array>
    //#include <unordered_map>
    //#include <complex>
    //#include <deque>
    #include <valarray>
     
    // stream
    //#include <istream>
    //#include <sstream>
    //#include <ostream>
    //#include <fstream>
     
    // etc
    #include <cassert>
    #include <cmath>
    #include <functional>
    #include <iomanip>
    #include <chrono>
    #include <random>
    #include <numeric>
     
    // input
    #define INIT std::ios::sync_with_stdio(false);std::cin.tie(0);
    #define VAR(type, ...)type __VA_ARGS__;MACRO_VAR_Scan(__VA_ARGS__);
    template<typename T> void MACRO_VAR_Scan(T& t) { std::cin >> t; }
    template<typename First, typename...Rest>void MACRO_VAR_Scan(First& first, Rest&...rest) { std::cin >> first; MACRO_VAR_Scan(rest...); }
    #define VEC_ROW(type, n, ...)std::vector<type> __VA_ARGS__;MACRO_VEC_ROW_Init(n, __VA_ARGS__); for(int i=0; i<n; ++i){MACRO_VEC_ROW_Scan(i, __VA_ARGS__);}
    template<typename T> void MACRO_VEC_ROW_Init(int n, T& t) { t.resize(n); }
    template<typename First, typename...Rest>void MACRO_VEC_ROW_Init(int n, First& first, Rest&...rest) { first.resize(n); MACRO_VEC_ROW_Init(n, rest...); }
    template<typename T> void MACRO_VEC_ROW_Scan(int p, T& t) { std::cin >> t[p]; }
    template<typename First, typename...Rest>void MACRO_VEC_ROW_Scan(int p, First& first, Rest&...rest) { std::cin >> first[p]; MACRO_VEC_ROW_Scan(p, rest...); }
    #define VEC(type, c, n) std::vector<type> c(n);for(auto& i:c)std::cin>>i;
    #define MAT(type, c, m, n) std::vector<std::vector<type>> c(m, std::vector<type>(n));for(auto& r:c)for(auto& i:r)std::cin>>i;
     
    // output
    #define OUT(d) std::cout<<d;
    #define FOUT(n, d) std::cout<<std::fixed<<std::setprecision(n)<<d;
    #define SOUT(n, c, d) std::cout<<std::setw(n)<<std::setfill(c)<<d;
    #define SP std::cout<<" ";
    #define TAB std::cout<<"\t";
    #define BR std::cout<<"\n";
    #define SPBR(i, n) std::cout<<(i + 1 == n ? '\n' : ' ');
    #define ENDL std::cout<<std::endl;
    #define FLUSH std::cout<<std::flush;
    #define SHOW(d) {std::cerr << #d << "\t:" << d << "\n";}
    #define SHOWVECTOR(v) {std::cerr << #v << "\t:";for(const auto& xxx : v){std::cerr << xxx << " ";}std::cerr << "\n";}
    #define SHOWVECTOR2(v) {std::cerr << #v << "\t:\n";for(const auto& xxx : v){for(const auto& yyy : xxx){std::cerr << yyy << " ";}std::cerr << "\n";}}
    #define SHOWQUEUE(a) {auto tmp(a);std::cerr << #a << "\t:";while(!tmp.empty()){std::cerr << tmp.front() << " ";tmp.pop();}std::cerr << "\n";}
     
    // utility
    #define ALL(a) (a).begin(),(a).end()
    #define FOR(i, a, b) for(int i=(a);i<(b);++i)
    #define RFOR(i, a, b) for(int i=(b)-1;i>=(a);--i)
    #define REP(i, n) for(int i=0;i<int(n);++i)
    #define RREP(i, n) for(int i=int(n)-1;i>=0;--i)
    #define FORLL(i, a, b) for(ll i=ll(a);i<ll(b);++i)
    #define RFORLL(i, a, b) for(ll i=ll(b)-1;i>=ll(a);--i)
    #define REPLL(i, n) for(ll i=0;i<ll(n);++i)
    #define RREPLL(i, n) for(ll i=ll(n)-1;i>=0;--i)
    #define IN(a, x, b) (a<=x && x<b)
    template<typename T> inline T CHMAX(T& a, const T b) { return a = (a < b) ? b : a; }
    template<typename T> inline T CHMIN(T& a, const T b) { return a = (a > b) ? b : a; }
    #define EXCEPTION(msg) throw std::string("Exception : " msg " [ in ") + __func__ + " : " + std::to_string(__LINE__) + " lines ]"
    #define TRY(cond, msg) try {if (cond) EXCEPTION(msg);}catch (std::string s) {std::cerr << s << std::endl;}
    void CHECKTIME(std::function<void()> f) { auto start = std::chrono::system_clock::now(); f(); auto end = std::chrono::system_clock::now(); auto res = std::chrono::duration_cast<std::chrono::nanoseconds>((end - start)).count(); std::cerr << "[Time:" << res << "ns  (" << res / (1.0e9) << "s)]\n"; }
     
    // test
    template<class T> std::vector<std::vector<T>> VV(int n) {
    	return std::vector<std::vector<T>>(n);
    }
    template<class T> std::vector<std::vector<T>> VV(int n, int m, T init = T()) {
    	return std::vector<std::vector<T>>(n, std::vector<T>(m, init));
    }
    template<typename S, typename T>
    std::ostream& operator<<(std::ostream& os, std::pair<S, T> p) {
    	os << "(" << p.first << ", " << p.second << ")"; return os;
    }
     
    // type/const
     
    #define int ll
    using ll = long long;
    using ull = unsigned long long;
    using ld = long double;
    using PAIR = std::pair<int, int>;
    using PAIRLL = std::pair<ll, ll>;
    constexpr int INFINT = 1 << 30;                          // 1.07x10^ 9
    constexpr int INFINT_LIM = (1LL << 31) - 1;              // 2.15x10^ 9
    constexpr ll INFLL = 1LL << 60;                          // 1.15x10^18
    constexpr ll INFLL_LIM = (1LL << 62) - 1 + (1LL << 62);  // 9.22x10^18
    constexpr double EPS = 1e-9;
    constexpr int MOD = 1000000007;
    constexpr double PI = 3.141592653589793238462643383279;
     
    signed main() {
    	INIT;
    	VAR(int, n, z, w);
    	VEC(int, a, n);
    	int ans = std::abs(w - a[n - 1]);
    	if (n > 1) CHMAX(ans, std::abs(a[n - 2] - a[n - 1]));
    	OUT(ans)BR;
    	return 0;
    }

Measured memory_bytes: 256