/**
 * code generated by JHelper
 * More info: https://github.com/AlexeyDmitriev/JHelper
 * @author Majk
 */

#include <vector>
#include <iostream>
#include <unordered_map>
#include <map>
#include <iomanip>
#include <set>
#include <functional>
#include <fstream>
#include <algorithm>
#include <cassert>
#include <cmath>
#include <string>
#include <sstream>
#include <queue>
using namespace std;

#define x first
#define y second
constexpr int MOD = 1000000007;

typedef std::pair<int,int> pii;
typedef long long ll;
typedef unsigned int ui;

template<typename T>std::istream&operator>>(std::istream&i,vector<T>&t) {for(auto&v:t){i>>v;}return i;}
template<typename T>std::ostream&operator<<(std::ostream&o,const vector<T>&t) {for(size_t i=0;i<t.size();++i){o<<t[i]<<" \n"[i == t.size()-1];}return o;}
template <typename T, typename U> std::istream&operator>>(std::istream&i, pair<T,U>&p) {i >> p.x >> p.y; return i;}
template<typename T> using minheap = priority_queue<T, vector<T>, greater<T>>;
template<typename T> using maxheap = priority_queue<T, vector<T>, less<T>>;

struct input {
	std::istream &cin;
	explicit input(std::istream &cin) :cin(cin){}
	template <typename T> operator T() { T t; cin >> t; return t; }
};
#define $ input{cin}

int logceil(ll x) {int b=0;while(x){x>>=1;++b;}return b;}

namespace std {
    template<typename T,typename U>struct hash<pair<T,U>>{hash<T>t;hash<U>u;size_t operator()(const pair<T,U>&p)const{return t(p.x)^(u(p.y)<<7);}};
}
template<typename T,typename F>T bsh(T l,T h,const F&f){T r=-1,m;while(l<=h){m=(l+h)/2;if(f(m)){l=m+1;r=m;}else{h=m-1;}}return r;}
template<typename T,typename F>T bsl(T l,T h,const F&f){T r=-1,m;while(l<=h){m=(l+h)/2;if(f(m)){h=m-1;r=m;}else{l=m+1;}}return r;}
template<typename T> T gcd(T a,T b) { if (a<b) swap(a,b); return b?gcd(b,a%b):a; }

template<typename T>class vector2:public vector<vector<T>>{public:vector2(){} vector2(size_t a,size_t b,T t=T()):vector<vector<T>>(a,vector<T>(b,t)){}};
template<typename T>class vector3:public vector<vector<vector<T>>>{public:vector3(){} vector3(size_t a,size_t b,size_t c,T t=T()):vector<vector<vector<T>>>(a,vector<vector<T>>(b,vector<T>(c,t))){}};

// #include "../l/mod.h"

class F {
public:
    void solve(istream& cin, ostream& cout) {
		int N, Q, A, B;
		cin >> N >> Q >> A >> B;
		vector<int> X(Q);
		cin >> X;
		unordered_map<pii, ll> R;
		R[{min(A, B), max(A, B)}] = (ll) N * Q;
		for (int i = 0; i < Q; ++i) {
			unordered_map<pii, ll> S;
			for (auto it = R.begin(); it != R.end(); ++it) {
				if (X[i] <= it->x.x) S[{X[i], it->x.y}] = max(S[{X[i], it->x.y}], it->y - it->x.x + X[i]);
				else if (X[i] >= it->x.y) S[{it->x.x, X[i]}] = max(S[{it->x.x, X[i]}], it->y - X[i] + it->x.y);
				else {
					S[{X[i], it->x.y}] = max(S[{X[i], it->x.y}], it->y - X[i] + it->x.x);
					S[{it->x.x, X[i]}] = max(S[{it->x.x, X[i]}], it->y - it->x.y + X[i]);
				}
			}

			swap(R, S);
		}

		ll ans = 0;
		for (auto it = R.begin(); it != R.end(); ++it) {
			ans = max(ans, it->y);
		}
		cout << (ll)N*Q - ans << endl;
	}
};


int main() {
	ios_base::sync_with_stdio(false); cin.tie(nullptr); cout.tie(nullptr);
	F solver;
	std::istream& in(std::cin);
	std::ostream& out(std::cout);
	solver.solve(in, out);
	return 0;
}



Measured memory_bytes: 1024