uses crt;
var x1,y1,x2,y2,x3,y3,a,b,c,p:real;
function d(x1,y1,x2,y2:real):real;
begin
d:=sqrt(sqr(x2-x1)+sqr(y2-y1));
end;
begin
clrscr;
write('X1 Y1 X2 Y2 X3 Y3 -> ');
readln(x1,y1,x2,y2,x3,y3);
a:=d(x1,y1,x2,y2);
b:=d(x1,y1,x3,y3);
c:=d(x3,y3,x2,y2);
if not ((a<b+c) and (b<a+c) and (c<a+b)) then write('Такого тр-ка не существует!') else
begin
p:=a+b+c;
writeln('P=',p:0:4);
end;
readln;
end.