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 =110;
#define clc(a,b) memset(a,b,sizeof(a))
const double eps = 1e-8;
void fre() {freopen("in.txt","r",stdin);}
void freout() {freopen("out.txt","w",stdout);}
inline int read() {int x=0,f=1;char ch=getchar();while(ch>'9'||ch<'0') {if(ch=='-') f=-1; ch=getchar();}while(ch>='0'&&ch<='9') {x=x*10+ch-'0';ch=getchar();}return x*f;}

int sgn(double x){
    if(fabs(x) < eps)return 0;
    if(x < 0)return -1;
    else return 1;
}

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=0;
        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)/2+1);
    }
    return 0;
}