#include<bits/stdc++.h>
#define rep(i,n) for(int i=0;i<(int)n;i++)
#define all(c) (c).begin(),(c).end()
#define pb push_back
#define dbg(...) do{cerr<<__LINE__<<": ";dbgprint(#__VA_ARGS__, __VA_ARGS__);}while(0);

using namespace std;

namespace std{template<class S,class T>struct hash<pair<S,T>>{size_t operator()(const pair<S,T>&p)const{return ((size_t)1e9+7)*hash<S>()(p.first)+hash<T>()(p.second);}};template<class T>struct hash<vector<T>>{size_t operator()(const vector<T> &v)const{size_t h=0;for(auto i : v)h=h*((size_t)1e9+7)+hash<T>()(i)+1;return h;}};}
template<class T>ostream& operator<<(ostream &os, const vector<T> &v){os<<"[ ";rep(i,v.size())os<<v[i]<<(i==v.size()-1?" ]":", ");return os;}template<class T>ostream& operator<<(ostream &os,const set<T> &v){os<<"{ "; for(const auto &i:v)os<<i<<", ";return os<<"}";}
template<class T,class U>ostream& operator<<(ostream &os,const map<T,U> &v){os<<"{";for(const auto &i:v)os<<" "<<i.first<<": "<<i.second<<",";return os<<"}";}template<class T,class U>ostream& operator<<(ostream &os,const pair<T,U> &p){return os<<"("<<p.first<<", "<<p.second<<")";}
void dbgprint(const string &fmt){cerr<<endl;}template<class H,class... T>void dbgprint(const string &fmt,const H &h,const T&... r){cerr<<fmt.substr(0,fmt.find(","))<<"= "<<h<<" ";dbgprint(fmt.substr(fmt.find(",")+1),r...);}
typedef long long ll;typedef vector<int> vi;typedef pair<int,int> pi;const int inf = (int)1e9;const double INF = 1e12, EPS = 1e-9;
template<class T>struct SegTree{
	T *dat, *lazy;
	int n;
	SegTree(int size = 1000000){
		for(n = 1; n < size; n *= 2);
		dat = new T[2 * n - 1];
		lazy= new T[2 * n - 1];
		init();
	}
	~SegTree(){ delete [] dat; delete [] lazy; }
	
	void init(){
		rep(i, 2 * n - 1) dat[i] = 0;
		rep(i, 2 * n - 1) lazy[i]= 0;
	}
	void add(int a, int b, ll v, int k, int l, int r){
		if(r <= a || b <= l) return;
		if(a <= l && r <= b){ lazy[k] += v; return; }
		if(lazy[k]){
			lazy[k * 2 + 1] += lazy[k];
			lazy[k * 2 + 2] += lazy[k]; lazy[k] = 0;
		}
		add(a, b, v, k * 2 + 1, l, (l + r) / 2);
		add(a, b, v, k * 2 + 2, (l + r) / 2, r);
		dat[k] = min(dat[k * 2 + 1] + lazy[k * 2 + 1], dat[k * 2 + 2] + lazy[k * 2 + 2]);
	}
	T query(int a, int b, int k, int l, int r){
		if(r <= a || b <= l) return 1e17;
		if(a <= l && r <= b) return dat[k] + lazy[k];
		if(lazy[k]){
			lazy[k * 2 + 1] += lazy[k];
			lazy[k * 2 + 2] += lazy[k]; lazy[k] = 0;
		}
		T vl = query(a, b, k * 2 + 1, l, (l + r) / 2);
		T vr = query(a, b, k * 2 + 2, (l + r) / 2, r);
		dat[k] = min(dat[k * 2 + 1] + lazy[k * 2 + 1], dat[k * 2 + 2] + lazy[k * 2 + 2]);
		return min(vl, vr);
	}
	T query(int a, int b){ return query(a, b, 0, 0, n); }
	void add(int a, int b, ll v){ add(a, b, v, 0, 0, n); }
	void chmin(int a, ll v){
		ll prev = query(a, a + 1);
		if(prev > v) add(a, a + 1, v - prev);
	}
};
int main(){
	cin.tie(0); cin.sync_with_stdio(0);
	
	int n, q, a, b; cin >> n >> q >> a >> b;
	vi x(q + 1); rep(i, q) cin >> x[i + 1];
	x[0] = a;
	
	SegTree<ll> *seg1 = new SegTree<ll>(n + 1);
	SegTree<ll> *seg2 = new SegTree<ll>(n + 1);
	SegTree<ll> &dp1 = *seg1, &dp2 = *seg2;
	
	dp1.add(0, n + 1, inf);
	dp2.add(0, n + 1, inf);
	
	dp1.chmin(b, -b);
	dp2.chmin(b, b);
	rep(i, q){
		ll mn = 1e18;
		mn = min(mn, dp1.query(0, x[i + 1] + 1) + x[i + 1]);
		mn = min(mn, dp2.query(x[i + 1], n + 1) - x[i + 1]);
		dp1.add(0, n + 1, abs(x[i + 1] - x[i]));
		dp2.add(0, n + 1, abs(x[i + 1] - x[i]));
		dp1.chmin(x[i], mn - x[i]);
		dp2.chmin(x[i], mn + x[i]);
	}
	ll ans = 1e18;
	rep(i, n + 1) ans = min(ans, dp1.query(i, i + 1) + i);
	rep(i, n + 1) ans = min(ans, dp2.query(i, i + 1) - i);
	cout << ans << endl;
	return 0;
}

Measured memory_bytes: 17408