#include <iostream>

 #include<cstdio>

 #include<cstring>

 #include<algorithm>

 #include<stdlib.h>

 #include<vector>

 #include<cmath>

 #include<queue>

 #include<set>

 using namespace std;

 #define N 100000

 #define LL long long

 #define INF 0xfffffff

 const double eps = 1e-;

 const double pi = acos(-1.0);

 const double inf = ~0u>>;

 struct Point

 {

     double x,y;

     Point(double x=,double y=):x(x),y(y) {}

 }p[];

 typedef Point pointt;

 pointt operator + (Point a,Point b)

 {

      return Point(a.x+b.x,a.y+b.y);

 }

 pointt operator - (Point a,Point b)

 {

         return Point(a.x-b.x,a.y-b.y);

 }

 int dcmp(double x)

 {

     if(fabs(x)<eps) return ;

     else return x<?-:;

 }

 struct Circle

 {

     Point center;

     double r;

 };

 double cross(Point a,Point b)

 {

     return a.x*b.y-a.y*b.x;

 }

 double mul(Point p0,Point p1,Point p2)

 {

     return cross(p1-p0,p2-p0);

 }

 double dis(Point a)

 {

     return a.x*a.x+a.y*a.y;

 }

 double area()

 {

     return fabs(cross(p[]-p[],p[]-p[]))/;

 }

 bool seginter(pointt a1,pointt a2,pointt b1,pointt b2)

 {

      double c1 = cross(a2-a1,b1-a1),c2 = cross(a2-a1,b2-a1),

             c3 = cross(b2-b1,a1-b1),c4 = cross(b2-b1,a2-b1);

      return dcmp(c1)*dcmp(c2)<&&dcmp(c3)*dcmp(c4)<;

 }

 struct Circle Circumcircle()

 {

     Circle tmp;

     double a,b,c,c1,c2;

     double xa,ya,xb,yb,xc,yc;

     a = sqrt(dis(p[]-p[]));

     b = sqrt(dis(p[]-p[]));

     c = sqrt(dis(p[]-p[]));

     //根据s = a*b*c/R/4，求半径

     tmp.r = (a*b*c)/(area()*4.0);

     xa = p[].x;

     ya = p[].y;

     xb = p[].x;

     yb = p[].y;

     xc = p[].x;

     yc = p[].y;

     c1 = (dis(p[])-dis(p[]))/;

     c2 = (dis(p[])-dis(p[]))/;

     tmp.center.x = (c1*(ya-yc)-c2*(ya-yb))/((xa-xb)*(ya-yc)-(xa-xc)*(ya-yb));

     tmp.center.y = (c1*(xa-xc)-c2*(xa-xb))/((ya-yb)*(xa-xc)-(ya-yc)*(xa-xb));

     return tmp;

 }

 int main()

 {

     int i;

     double r;

     int w0,w1,h0,h1;

     for(i = ; i <=  ; i++)

     scanf("%lf%lf",&p[i].x,&p[i].y);

     Circle cc = Circumcircle();

     r = cc.r;

     Point q[];

     for(i =  ;i <  ;i++)

     q[i] = cc.center;

     q[].x-=r,q[].x+=r,q[].y-=r,q[].y+=r;

     if(!seginter(q[],p[],p[],p[])) w0 = floor(q[].x+eps);

     else w0 = floor(min(p[].x,p[].x)+eps);

     if(!seginter(q[],p[],p[],p[]))  w1 = ceil(q[].x-eps);

     else w1 = ceil(max(p[].x,p[].x)-eps);

     if(!seginter(q[],p[],p[],p[])) h0 = floor(q[].y+eps);

     else h0 = floor(min(p[].y,p[].y)+eps);

     if(!seginter(q[],p[],p[],p[])) h1 = ceil(q[].y-eps);

     else h1 = ceil(max(p[].y,p[].y)-eps);

     printf("%d\n",(h1-h0)*(w1-w0));

     return ;

 }