题目就是早从左到右的路

注意输入的实数

这题图画好就行，别像我一开始把图弄反就成

从上开始找，若找到一个与下边界相邻的就无解，找到与左边相邻的记圆与左边界相交的下边的点（相当于左上角挖去一块），右边同理。

Program snake;
const
   maxn=1000;
var
   n,i,j:longint;
   x,y,r,lc,rc:array[1..maxn] of double;
   maxl,maxr:double;
   father:array[1..maxn] of longint;
   b,up,down,left,right:array[1..maxn] of boolean;
function getfather(x:longint):longint;
begin
   if father[x]=x then exit(x);
   father[x]:=getfather(father[x]);
   exit(father[x]);
end;
Procedure union(x,y:longint);
begin
   father[father[x]]:=father[father[y]];
end;
function distance(i,j:longint):double;
begin
   exit(sqrt(sqr(x[i]-x[j])+sqr(y[i]-y[j])));
end;
function dis(x1,y1,x2,y2:double):double;
begin
   exit(sqrt(sqr(x1-x2)+sqr(y1-y2)));
end;

begin
   fillchar(b,sizeof(b),false);
   fillchar(up,sizeof(up),false);
   fillchar(down,sizeof(down),false);
   fillchar(left,sizeof(left),false);
   fillchar(right,sizeof(right),false);
   fillchar(lc,sizeof(lc),0);
   fillchar(rc,sizeof(rc),0);
   maxl:=1000;maxr:=1000;

   read(n);
   for i:=1 to n do
   begin
      read(x[i],y[i],r[i]);
      father[i]:=i;
      for j:=1 to i-1 do
         if distance(i,j)<r[i]+r[j] then
            if getfather(i)<>getfather(j) then
               union(i,j);
      if (y[i]<r[i]) then down[i]:=true;
      if (y[i]+r[i]>1000) then up[i]:=true;
      if (x[i]<r[i]) then
      begin
         left[i]:=true;
         lc[i]:=y[i]-sqrt(sqr(r[i])-sqr(x[i]));
      end;
      if (x[i]+r[i]>1000) then
      begin
         right[i]:=true;
         rc[i]:=y[i]-sqrt(sqr(r[i])-sqr(1000-x[i]));
      end;

   end;
   for i:=1 to n do
      if (up[i]) and not(b[i]) then
      begin
         for j:=1 to n do
            if father[i]=father[j] then
            begin
               b[j]:=true;
               if (down[j]) then
               begin
                  writeln('Bill will be bitten.');
                  halt;
               end;
               if left[j] then
               begin
                  if lc[j]<maxl then maxl:=lc[j];

               end;
               if right[j] then
               begin
                  if rc[j]<maxr then maxr:=rc[j];
               end;


            end;
      end;
   writeln('Bill enters at (0.00, ',maxl:2:2,') and leaves at (1000.00, ',maxr:2:2,').');




end.