#include<stdio.h>#include<math.h>double eps=1e-10;int dbcmp(double a){if(a>eps) return 1;else if(a<(-eps)) return -1;return 0;}struct point{point(){x=y=0;}point(double a,double b){x=a;y=b;} double x,y;};double xmult(point p1,point p2,point p0){ return (p1.x-p0.x)*(p2.y-p0.y)-(p2.x-p0.x)*(p1.y-p0.y);}double distance(point p1,point p2){ return sqrt((p1.x-p2.x)*(p1.x-p2.x)+(p1.y-p2.y)*(p1.y-p2.y));}point intersection(point u1,point u2,point v1,point v2){ point ret=u1; double t=((u1.x-v1.x)*(v1.y-v2.y)-(u1.y-v1.y)*(v1.x-v2.x))/((u1.x-u2.x)*(v1.y-v2.y)-(u1.y-u2.y)*(v1.x-v2.x)); ret.x+=(u2.x-u1.x)*t; ret.y+=(u2.y-u1.y)*t; return ret;}double disptoline(point p,point l1,point l2){ return fabs(xmult(p,l1,l2))/distance(l1,l2);}void intersection_line_circle(point c,double r,point l1,point l2,point& p1,point& p2){ point p=c; double t; p.x+=l1.y-l2.y; p.y+=l2.x-l1.x; p=intersection(p,c,l1,l2); t=sqrt(r*r-distance(p,c)*distance(p,c))/distance(l1,l2); p1.x=p.x+(l2.x-l1.x)*t; p1.y=p.y+(l2.y-l1.y)*t; p2.x=p.x-(l2.x-l1.x)*t; p2.y=p.y-(l2.y-l1.y)*t;}int main(){double rm,R,r,x,y,vx,vy;while(scanf("%lf%lf%lf%lf%lf%lf%lf",&rm,&R,&r,&x,&y,&vx,&vy)!=EOF){double dist = disptoline(point(0,0),point(x,y),point(x+vx,y+vy));if(dbcmp(dist-R-r)>=0){printf("0n");continue;}point o1,o2;intersection_line_circle(point(0,0),R+r,point(x,y),point(x+vx,y+vy),o1,o2);o2.x=o1.x-x;o2.y=o1.y-y;double aa=o2.x*vx+o2.y*vy;if(dbcmp(aa)<0){printf("0n");continue;}if(dbcmp(dist-r-rm)>=0){point j1,j2;intersection_line_circle(point(0,0),R+r,point(x,y),point(x+vx,y+vy),j1,j2);double dx=j2.x-j1.x;double dy=j2.y-j1.y;double time;if(dbcmp(vy)!=0){time=dy/vy;}else{time=dx/vx;}if(dbcmp(time)<0){time=-time;}printf("%.3lfn",time);continue;}else{point j1,j2,j3,j4;intersection_line_circle(point(0,0),R+r,point(x,y),point(x+vx,y+vy),j1,j2);intersection_line_circle(point(0,0),rm+r,point(x,y),point(x+vx,y+vy),j3,j4);point a=j1,b;if(distance(a,j3)>distance(a,j4)){b=j4;}else{b=j3;}double dx=a.x-b.x,dy=a.y-b.y;double time;if(dbcmp(vy)!=0){time=dy/vy;}else{time=dx/vx;}if(dbcmp(time)<0){time=-time;}printf("%.3lfn",time*2);}}return 0;}
