I think my method to solve this problem is all right,but the
result is just WA.Anyone please tell me what is wrong or give me
some test cases,thanks a lot!And here is my program in C++:

#include<iostream.h>
#include<math.h>
#define eps 1e-7
#define pi 2*asin(1)
double a[3],b[3];
double x,y,r;
double s0,s1,s2;
double max(double m,double n)
{
    if(m-n<eps)return n;
    return m;
}
double min(double m,double n)
{
    if(n-m<eps)return n;
    return m;
}
void circle()
{
    x=(a[0]*a[0]+b[0]*b[0]-a[1]*a[1]-b[1]*b[1])/2*(b[0]-b[2]);
    x-=(a[0]*a[0]+b[0]*b[0]-a[2]*a[2]-b[2]*b[2])/2*(b[0]-b[1]);
    x/=(a[0]-a[1])*(b[0]-b[2])-(a[0]-a[2])*(b[0]-b[1]);
    y=(a[0]-a[1])*(a[0]*a[0]+b[0]*b[0]-a[2]*a[2]-b[2]*b[2])/2;
    y-=(a[0]-a[2])*(a[0]*a[0]+b[0]*b[0]-a[1]*a[1]-b[1]*b[1])/2;
    y/=(a[0]-a[1])*(b[0]-b[2])-(a[0]-a[2])*(b[0]-b[1]);
    r=sqrt((x-a[0])*(x-a[0])+(y-b[0])*(y-b[0]));
}
double angle(double m,double n)
{
    m-=x,n-=y;
    if(n>=0)return acos(m/r);
    n=-n;
    return 2*pi-acos(m/r);
}
int test(double s)
{
    if(s-max(s0,s1)<eps&&s-min(s0,s1)>=eps)return 1;
    else return 0;
}
void main()
{
    cin>>a[0]>>b[0];
    cin>>a[1]>>b[1];
    cin>>a[2]>>b[2];
    circle();
    s0=angle(a[0],b[0]);
    s1=angle(a[1],b[1]);
    s2=angle(a[2],b[2]);
    long mark=test(s2);
    double up,down,left,right;
    if(test(0)==mark){
        right=x+r;
    }
    else right=max(a[0],a[1]);
    if(test(pi/2)==mark){
        up=y+r;
    }
    else up=max(b[0],b[1]);
    if(test(pi)==mark){
        left=x-r;
    }
    else left=min(a[0],a[1]);
    if(test(3*pi/2)==mark){
        down=y-r;
    }
    else down=min(b[0],b[1]);
    mark=(long)ceil(up)-(long)floor(down);
    mark*=(long)ceil(right)-(long)floor(left);
    cout<<mark<<endl;
}