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 ;
 }