how to deal with this sentence 
The final line of input will contain only a -1.


if the input data is -1 0 0 3 4 5 , how to deal with it , i am puzzled
 
this is my program , i don't know what 's wrong with it, could hawk give me some data to test it ?
thanks.




#include<iostream>
#include<cmath>
using namespace std;
const double ang=3.1415926/2;
double A,B;

double dis(double x1, double x2, double y1, double y2){
	return sqrt((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2));
}

int main(){
	int i,j,k,angle,len;
	double x1,x2,x3,y1,y2,y3;
	A=ang*88.0/90;
	B=ang*92.0/90;

	bool ok=true;

	while(scanf("%lf",&x1)){
    	if (x1==-1) break;
		scanf("%lf%lf%lf%lf%lf",&y1,&x2,&y2,&x3,&y3);
	    
		double a,b,c;
		a=dis(x1,x2,y1,y2);
		b=dis(x1,x3,y1,y3);
		c=dis(x2,x3,y2,y3);
        int  ok1=0;
   //     cout<<a<<"  "<<b<<"  "<<c<<endl;
		double x,y,z;
		x=fabs(a-b);
		y=fabs(a-c);
		z=fabs(b-c);
//	    cout<<x<<"   "<<y<<"  "<<z<<endl;
        if (a<=0.00001||b<=0.00001||c<=0.00001||a+b-c<0.001||a+c-b<0.001||b+c-a<0.001) ok1=0;
        else  if (x<=0.01&&y<=0.01&&z<=0.01) ok1=3;
		else if (x<=0.01||y<=0.01||z<=0.01)ok1=2;
		else  ok1=1;
		
	//	cout<<ok1<<endl;
		if (ok1>0){  
			double u,v,w;
			u=acos((a*a+b*b-c*c)/(2*a*b));
			v=acos((a*a+c*c-b*b)/(2*a*c));
			w=acos((b*b+c*c-a*a)/(2*b*c));
			int  ok2=0;
         //  cout<<"A: "<<A<<"     "<<"B: "<<B<<endl;
	     //   cout<<u<<"  "<<v<<"  "<<w<<endl;
			if ((u>=A&&u<=B)||(v>=A&&v<=B)||(w>=A&&v<=B)) ok2=2;
			else if (u<A&&v<A&&w<A) ok2=1;
			else ok2=0;
          //  cout<<ok2<<endl;
			if (ok1==1) printf("Scalene");
			else if (ok1==2) printf("Isosceles");
			else printf("Equilateral");
 
			if (ok2==1) printf(" Acute\n");
			else if (ok2==2) printf(" Right\n");
			else printf(" Obtuse\n");
		                           
		}
		else printf("Not a Triangle\n");
	}
	printf("End of Output\n");
	return 0;
}