#define f(x,y)(x[j]-x[k])*(y[i]-y[k])-(y[j]-y[k])*(x[i]-x[k]),
double x[301],y[301],z[301],p,q,r,s;k=-1,j;main(i){for(gets(&i);++j<k?p=f(y,z)q=f(z,x)r=f(x,y)s+=fabs(p*(*x-x[k])+q*(*y-y[k])+r*(*z-z[k]))/sqrt(p*p+q*q+r*r):(j=++i,i<k)?:(i=!++k,~scanf("%lf%lf%lf",x+k,y+k,z+k)););k=!printf("%f",s);}