#include <bits/stdc++.h>
using namespace std;
using ld = long double;
pair<ld,ld> nearest(int a, int b, int c, int d, int x, int y) {
pair<ld,ld> ln1 = {(d-b)/ld(c-a), 0};
ln1.second = b - ln1.first * a;
pair<ld,ld> ln2 = {-1/ln1.first,0};
ln2.second = y - ln2.first * x;
pair<ld,ld> isect = {0,0};
isect.first = (ln2.second - ln1.second) / (ln1.first - ln2.first);
if(isect.first < a && isect.first < c)
isect.first = min(a, c);
if(isect.first > a && isect.first > c)
isect.first = max(a, c);
isect.second = ln1.first * isect.first + ln1.second;
return isect;
}
ld dist(ld x, ld y) {return sqrt(x * x + y * y);}
ld tot(int a, int b, int c, int d, int x1, int y1, int x2, int y2) {
pair<ld,ld> p1 = nearest(a,b,c,d,x1,y1);
pair<ld,ld> p2 = nearest(a,b,c,d,x2,y2);
return dist(p1.first-p2.first,p1.second-p2.second)+dist(x1-p1.first,y1-p1.second)+dist(x2-p2.first,y2-p2.second);
}
int main() {
int n, s, a, b, c, d;
cin >> n >> s;
cin >> a >> b >> c >> d;
if(a == c || b == d) {
cout << 8 * s;
return 0;
}
ld ans = 0;
ans = min(ans, tot(a,b,c,d,s,s,s,-s) - 2*s);
ans = min(ans, tot(a,b,c,d,s,-s,-s,-s) - 2*s);
ans = min(ans, tot(a,b,c,d,-s,-s,-s,s) - 2*s);
ans = min(ans, tot(a,b,c,d,-s,s,s,s) - 2*s);
ans = min(ans, tot(a,b,c,d,s,s,-s,-s) - 4*s);
ans = min(ans, tot(a,b,c,d,s,-s,-s,s) - 4*s);
cout << fixed << setprecision(10) << (ans + 8 * s);
}
