//#include <bits/stdc++.h>
#include "bits/stdc++.h"
using namespace std;
typedef long long ll;


#include "boost/multiprecision/cpp_int.hpp"
#include "boost/multiprecision/cpp_dec_float.hpp"
namespace mp = boost::multiprecision;
typedef mp::cpp_int LL;
typedef mp::number<mp::cpp_dec_float<1024>> DD;// 仮数部が1024ビットの浮動小数点数型(TLEしたら小さくする)


typedef long double dd;
//#define i_7 (ll)(1E9+7)
#define i_7 998244353
#define i_5 i_7-2
ll mod(ll a){
    ll c=a%i_7;
    if(c>=0)return c;
    return c+i_7;
}
typedef pair<ll,ll> l_l;
typedef pair<dd,dd> d_d;
ll inf=(ll)1E16;
#define rep(i,l,r) for(ll i=l;i<=r;i++)
#define pb push_back
ll max(ll a,ll b){if(a<b)return b;else return a;}
ll min(ll a,ll b){if(a>b)return b;else return a;}
void Max(ll &pos,ll val){pos=max(pos,val);}//Max(dp[n],dp[n-1]);
void Min(ll &pos,ll val){pos=min(pos,val);}
void Add(ll &pos,ll val){pos=mod(pos+val);}
dd EPS=1E-9;
#define fastio ios::sync_with_stdio(false); cin.tie(0); cout.tie(0);
#define fi first
#define se second
#define endl "\n"
#define SORT(v) sort(v.begin(),v.end())
#define ERASE(v) v.erase(unique(v.begin(),v.end()),v.end())
#define POSL(v,x) (lower_bound(v.begin(),v.end(),x)-v.begin())
#define POSU(v,x) (upper_bound(v.begin(),v.end(),x)-v.begin())
template<class T,class S>
inline bool chmax(T &a, S b) {
    if(a < b) {
        a = b;
        return true;
    }
    return false;
}
template<class T,class S>
inline bool chmin(T &a, S b) {
    if(a > b) {
        a = b;
        return true;
    }
    return false;
}

void mod_print(ll k){
    ll P=1000;
    rep(y,1,P){
        ll x=mod(y*k);
        if(x+P>=i_7){
            x-=i_7;
        }
        if(abs(x)<=P){
            cout<<x<<"/"<<y<<endl;
            return;
        }
    }
    cout<<"nun"<<endl;
}
#define all(c) c.begin(),c.end()
//////////////////////////



//from betrue12 Codeforces 1326E
template<typename F, typename T, typename Func_mf, typename Func_op, typename Func_mv>
struct LazySegtree {
    ll n, n_org;
    vector<T> dat;
    vector<F> laz;
    Func_mf merge_functions; //lazyとlazyの演算
    Func_op operate;       //dataとlazyの演算
    Func_mv merge_values;  //dataとdataの演算
    F fe; //lazyの単位元かつ初期値
    T te; //dataの単位元かつ初期値
 
    LazySegtree(){}
    LazySegtree(ll n_org,
                Func_mf merge_functions,
                Func_op operate,
                Func_mv merge_values,
                F fe, T te):
                n_org(n_org),
                merge_functions(merge_functions),
                operate(operate),
                merge_values(merge_values),
                fe(fe), te(te){
        n = 1;
        while(n < n_org) n <<= 1;
        dat.resize(2*n-1, te);
        laz.resize(2*n-1, fe);
    }
 
    void build(vector<T>& A){
        for(ll k=0; k<ll(A.size()); k++) dat[k+n-1] = A[k];
        for(ll k=n-2; k>=0; k--) dat[k] = merge_values(dat[2*k+1], dat[2*k+2]);
    }
    void update(ll a, ll b, F x){ //[a,b]をupdate
        update(a, b+1, x, 0, 0, n);
    }
    T get(ll a, ll b){ //[a,b]から(最小値とか和とかを)get
        return query(a, b+1, 0, 0, n);
    }
 
    
private:
    void eval(ll k, ll w){
        if(laz[k] == fe) return;
        operate(dat[k], laz[k], w);
        if(k < n-1){
            merge_functions(laz[2*k+1], laz[k]);
            merge_functions(laz[2*k+2], laz[k]);
        }
        laz[k] = fe;
    }
    T query(ll a, ll b, ll k, ll lb, ll rb){
        eval(k, rb-lb);
        if(rb<=a || b<=lb) return te;
        if(a<=lb && rb<=b) return dat[k];
        ll mb = (lb+rb)>>1;
        T vl = query(a, b, 2*k+1, lb, mb);
        T vr = query(a, b, 2*k+2, mb, rb);
        return merge_values(vl, vr);
    }
    void update(ll a, ll b, F x, ll k, ll lb, ll rb){
        eval(k, rb-lb);
        if(b <= lb || rb <= a) return;
        if(a <= lb && rb <= b){
            merge_functions(laz[k], x);
            eval(k, rb-lb);
        }else{
            ll mb = (lb+rb)>>1;
            update(a, b, x, 2*k+1, lb, mb);
            update(a, b, x, 2*k+2, mb, rb);
            dat[k] = merge_values(dat[2*k+1], dat[2*k+2]);
        }
    }
};
auto make_segtree = [](ll N){
    //区間加算と区間最小
    
    using F = ll;
    using T = ll;
    auto merge_functions = [](F& f, F& g){f += g;};
    auto operate = [](T& v, F& f, ll w){v += f;};
    auto merge_values = [](T& a, T& b){return min(a, b);};
    F fe = 0;
    T te = inf;
    
    return LazySegtree<F, T, decltype(merge_functions), decltype(operate), decltype(merge_values)>
        (N, merge_functions, operate, merge_values, fe, te);
};




int main(){fastio

    
    ll n,q,a,b;cin>>n>>q>>a>>b;
    ll x[q+1];
    x[0]=a;
    rep(i,1,q)cin>>x[i];
    auto ep=make_segtree(n+1);
    auto fp=make_segtree(n+1);
    
    vector<ll>init(n+1);
    rep(i,0,n)init[i]=inf/2;
    init[b]=b;ep.build(init);
    init[b]=-b;fp.build(init);
    
    rep(i,1,q){
        ll val=min(ep.get(x[i],n)-x[i],fp.get(1,x[i])+x[i]);
        
        ep.update(1,n,abs(x[i]-x[i-1]));
        fp.update(1,n,abs(x[i]-x[i-1]));
        
        
        ll j=x[i-1];
        if(ep.get(j,j)>val+j){
            
            ll vale=ep.get(j,j);
            ll sm=val-vale+j;
            ep.update(j,j,sm);
        }
        if(fp.get(j,j)>val-j){
            ll valf=fp.get(j,j);
            fp.update(j,j,val-valf-j);
        }
        //cout<<"ep"<<i<<":";rep(j,1,n)cout<<ep.get(j,j)-j<<" ";cout<<endl;
        //cout<<"fp"<<i<<":";rep(j,1,n)cout<<fp.get(j,j)+j<<" ";cout<<endl;
    }
    ll ans[n+1];
    rep(i,1,n)ans[i]=ep.get(i,i)-i;
   // rep(i,1,n)cout<<ans[i]<<" ";cout<<endl;
    ll t=inf;
    rep(i,1,n)chmin(t,ans[i]);
    cout<<t<<endl;
    
    return 0;
}





Measured memory_bytes: 21888