pick定理：面积=内部整数点数+边上整数点数/2-1

 //pick定理：面积=内部整数点数+边上整数点数/2-1

 // POJ 2954

 #include <iostream>

 #include <cstdio>

 #include <cstdlib>

 #include <algorithm>

 #include <vector>

 #include <math.h>

 using namespace std;

 #define LL long long

 typedef pair<int,int> pii;

 const double inf = 0x3f3f3f3f;

 const LL MOD =100000000LL;

 const int N =;

 #define clc(a,b) memset(a,b,sizeof(a))

 const double eps = 1e-;

 void fre() {freopen("in.txt","r",stdin);}

 void freout() {freopen("out.txt","w",stdout);}

 inline int read() {int x=,f=;char ch=getchar();while(ch>''||ch<'') {if(ch=='-') f=-; ch=getchar();}while(ch>=''&&ch<='') {x=x*+ch-'';ch=getchar();}return x*f;}

 int sgn(double x){

     if(fabs(x) < eps)return ;

     if(x < )return -;

     else return ;

 }

 struct Point{

     int x,y;

     Point(){}

     Point(int _x,int _y){

         x = _x;y = _y;

     }

     Point operator -(const Point &b)const{

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

     }

     int operator ^(const Point &b)const{

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

     }

     int operator *(const Point &b)const{

         return x*b.x + y*b.y;

     }

     friend bool operator<(const Point &a,const Point &b){

         if(fabs(a.y-b.y)<eps) return a.x<b.x;

         return a.y<b.y;

     }

 };

 int area(Point a,Point b,Point c){

     return fabs((a-c)^(b-c));

 }

 //求多边形边上整点的数目，顶点必须为整数点

 int fun(Point a,Point b){

     int x,y;

     x=abs(a.x-b.x);

     y=abs(a.y-b.y);

     return __gcd(x,y);

 }

 int main(){

     // fre();

     int x1,y1,x2,y2,x3,y3;

     while(~scanf("%d%d%d%d%d%d",&x1,&y1,&x2,&y2,&x3,&y3),x1||x2||x3||y1||y2||y3){

         int ans=area(Point(x1,y1),Point(x2,y2),Point(x3,y3));

         int cnt=;

         Point a,b,c;

         a=Point(x1,y1);

         b=Point(x2,y2);

         c=Point(x3,y3);

         cnt+=fun(a,b);

         cnt+=fun(a,c);

         cnt+=fun(b,c);

         printf("%d\n",(ans-cnt)/+);

     }

     return ;

 }