// Slower C++ solution:
#include <bits/stdc++.h>



using namespace std;



template <class T> bool minimize(T &x, const T &y) {

    if (x > y) x = y; else return false; return true;

}



typedef long long ll;



const int N = 2e5 + 10;



int n, m, A, B;

int a[N];

ll s[N], bit1[N], bit2[N], f[N];



void upbit1(int x, ll para) {

    for (; x <= n; x += x & -x)

        minimize(bit1[x], para);

}



ll getbit1(int x) {

    ll ret = (ll)(1e16);

    for (; x; x -= x & -x)

        minimize(ret, bit1[x]);

    return ret;

}



void upbit2(int x, ll para) {

    for (; x; x -= x & -x)

        minimize(bit2[x], para);

}



ll getbit2(int x) {

    ll ret = (ll)(1e16);

    for (; x <= n; x += x & -x)

        minimize(ret, bit2[x]);

    return ret;

}



int main() {

    ios_base::sync_with_stdio(0); cin.tie(0);

    cin >> n >> m >> A >> B;

    for (int i = 1; i <= m; i++)

        cin >> a[i];

    /// init

    for (int i = 2; i <= m; i++) {

        s[i] = s[i - 1] + (ll)(abs(a[i] - a[i - 1]));

        /// A B

        f[i] = 1ll * abs(B - a[i]) + 1ll * abs(A - a[1]) + s[i - 1];

        /// B A

        f[i] = min(f[i], 1ll * abs(A - a[i]) + 1ll * abs(B - a[1]) + s[i - 1]);

    }

    memset(bit1, 60, sizeof(bit1));

    memset(bit2, 60, sizeof(bit2));

    /// dp

    for (int i = 2; i <= m; i++) {

        /// ai >= aj

        minimize(f[i], getbit1(a[i]) + (ll)(a[i]) + s[i - 1]);

        /// ai < aj

        minimize(f[i], getbit2(a[i] + 1) - (ll)(a[i]) + s[i - 1]);

        /// update

        upbit1(a[i - 1], f[i] - s[i] - (ll)(a[i - 1]));

        upbit2(a[i - 1], f[i] - s[i] + (ll)(a[i - 1]));

    }

    ll res = min(abs(a[1] - A), abs(a[1] - B)) + s[m];

    for (int i = 2; i <= m; i++)

        minimize(res, f[i] + s[m] - s[i]);

    cout << res;

}


// Faster C++ solution for the same problem (measured speedup: 21.587741111396774x):
#include<cstdio>

#include<cstring>

#include<algorithm>

using namespace std;

inline int gi()

{

	char c;int num=0,flg=1;

	while((c=getchar())<'0'||c>'9')if(c=='-')flg=-1;

	while(c>='0'&&c<='9'){num=num*10+c-48;c=getchar();}

	return num*flg;

}

#define N 200005

#define LL long long

#define lc i<<1

#define rc i<<1|1

const LL INF=0x3f3f3f3f3f3f3f3fll;

int pos[N],A,B,n,Q;

struct node{

	int l,r;

	LL mi1,mi2,la;

}a[N<<2];

void cal(int i,LL k){a[i].mi1+=k;a[i].mi2+=k;a[i].la+=k;}

void pushdown(int i)

{

	if(a[i].la&&a[i].l<a[i].r){

		cal(lc,a[i].la);cal(rc,a[i].la);

		a[i].la=0;

	}

}

void pushup(int i)

{

	a[i].mi1=min(a[lc].mi1,a[rc].mi1);

	a[i].mi2=min(a[lc].mi2,a[rc].mi2);

}

void build(int i,int l,int r)

{

	a[i].l=l;a[i].r=r;

	if(l==r){

		a[i].mi1=INF;a[i].mi2=INF;

		return;

	}

	int mid=(l+r)>>1;

	build(lc,l,mid);build(rc,mid+1,r);

	pushup(i);

}

void insert(int i,int l,int r,LL k)

{

	if(a[i].l>r||a[i].r<l)return;

	pushdown(i);

	if(l<=a[i].l&&a[i].r<=r){cal(i,k);return;}

	insert(lc,l,r,k);insert(rc,l,r,k);

	pushup(i);

}

void modify(int i,int x,LL k)

{

	if(a[i].l>x||a[i].r<x)return;

	pushdown(i);

	if(x==a[i].l&&a[i].r==x){a[i].mi1=min(a[i].mi1,k-x);a[i].mi2=min(a[i].mi2,k+x);return;}

	modify(lc,x,k);modify(rc,x,k);

	pushup(i);

}

LL query1(int i,int l,int r)

{

	if(a[i].l>r||a[i].r<l)return INF;

	pushdown(i);

	if(l<=a[i].l&&a[i].r<=r)return a[i].mi1;

	return min(query1(lc,l,r),query1(rc,l,r));

}

LL query2(int i,int l,int r)

{

	if(a[i].l>r||a[i].r<l)return INF;

	pushdown(i);

	if(l<=a[i].l&&a[i].r<=r)return a[i].mi2;

	return min(query2(lc,l,r),query2(rc,l,r));

}

LL query(int i)

{

	if(a[i].l==a[i].r)return a[i].mi1+a[i].l;

	pushdown(i);

	return min(query(lc),query(rc));

}

int ab(int x){return x<0?-x:x;}

int main()

{

	int i;LL f;

	n=gi();Q=gi();A=gi();B=gi();

	build(1,1,n);

	pos[0]=A;modify(1,B,0);

	for(i=1;i<=Q;i++){

		pos[i]=gi();

		f=min(query1(1,1,pos[i])+pos[i],query2(1,pos[i]+1,n)-pos[i]);

		insert(1,1,n,ab(pos[i]-pos[i-1]));

		modify(1,pos[i-1],f);

	}

	printf("%lld\n",query(1));

}