POJ 2954

#include <iostream>
#include <cstdio>
#include <cstring>
#include <cmath>
#include <algorithm>

using namespace std;

int x1,x2,x3,yy1,y2,y3;

int main(){
	while(cin>>x1>>yy1>>x2>>y2>>x3>>y3){
		if(x1==0&&yy1==0&&x2==0&&y2==0&&x3==0&&y3==0) break;
		double A=0.5 * abs((x1 - x3)*(y2 - yy1) - (x1 - x2)*(y3 - yy1));
		int k; int tmp=0;
		if(x1==x2)
		tmp+=(max(y2,yy1)-min(y2,yy1)+1);
		else {
			k=max(x1,x2);
			for(int i=min(x1,x2);i<=k;i++){
				if(((yy1-y2)*(i-x2))%(x1-x2)==0)
				tmp++;
			}
		}
		if(x1==x3)
		tmp+=(max(yy1,y3)-min(yy1,y3)+1);
		else{
			k=max(x1,x3);
			for(int i=min(x1,x3);i<=k;i++){
				if(((yy1-y3)*(i-x3))%(x1-x3)==0)
				tmp++;
			}
		}
		if(x2==x3)
		tmp+=(max(y2,y3)-min(y2,y3)+1);
		else{
			k=max(x2,x3);
			for(int i=min(x2,x3);i<=k;i++){
				if(((y2-y3)*(i-x3))%(x2-x3)==0)
				tmp++;
			}
		}
		tmp-=3;
		int ans=((A+1)*2-tmp)/2;
		cout<<ans<<endl;
	}
	return 0;
}