#include<stdio.h>#include<iostream>#include<string.h>#include<math.h>#include<algorithm>#include<queue>#include<set>#include<iterator>#include<map>
using namespace std;
int main()
{
int n, k;
scanf("%d%d", &n, &k);
intqx, qy;
scanf("%d%d", &qx, &qy);
int kx, ky;
int N = qx - 1;
int S = n - qx;
int W = qy - 1;
int E = n - qy;
int WN = W < N ? W : N;
int EN = E < N ? E : N;
int WS = W < S ? W : S;
int ES = E < S ? E : S;
for(int i = 0; i < k; i++){
scanf("%d%d", &kx, &ky);
if(kx == qx){
if(ky < qy) W = W < qy - ky - 1 ? W : qy - ky - 1;
elseif(ky > qy) E = E < ky - qy - 1 ? E : ky - qy - 1;
}
if(ky == qy){
if(kx < qx) N = N < qx - kx - 1 ? N : qx - kx - 1;
elseif(kx > qx) S = S < kx - qx - 1 ? S : kx - qx - 1;
}
if(kx-qx == ky-qy){
if(ky > qy) ES = ES < ky-qy-1 ? ES : ky-qy-1;
elseif(ky < qy) WN = WN < qy-ky-1 ? WN : qy-ky-1;
}
if(kx-qx == -(ky-qy)){
if(ky > qy) EN = EN < ky-qy-1 ? EN : ky-qy-1;
elseif(ky < qy) WS = WS < qy-ky-1 ? WS : qy-ky-1;
}
}
int ans = N+S+W+E+EN+WN+WS+ES;
printf("%d\n", ans);
return0;
}
/*
cout << endl;
cout << "1N: " << N << endl;
cout << "2S: " << S << endl;
cout << "3W: " << W << endl;
cout << "4E: " << E << endl;
cout << "5EN: " << EN << endl;
cout << "6WS: " << WS << endl;
cout << "7WN: " << WN << endl;
cout << "8ES: " << ES << endl;
*/