Расстояние от точки до отрезка

function dist(x1,y1,z1,x2,y2,z2: integer): real;
begin
  dist:=sqrt(sqr(x2-x1)+sqr(y2-y1)+sqr(z2-z1));
end;
 
var
  x1,y1,z1, x2,y2,z2, x3,y3,z3: integer;
  a,b,c: real;
  p,h: real;
begin
  write('Ââåäèòå 3 êîîðäèíàòû 1-é òî÷êè îòðåçêà: ');
  readln(x1,y1,z1);
  write('Ââåäèòå 3 êîîðäèíàòû 2-é òî÷êè îòðåçêà: ');
  readln(x2,y2,z2);
  write('Ââåäèòå 3 êîîðäèíàòû òî÷êè: ');
  readln(x3,y3,z3);
  a:=dist(x1,y1,z1,x2,y2,z2);
  b:=dist(x2,y2,z2,x3,y3,z3);
  c:=dist(x1,y1,z1,x3,y3,z3);
  p:=(a+b+c)/2;
  h:=2*sqrt(p*(p-a)*(p-b)*(p-c))/a;
  writeln('Ðàññòîÿíèå îò òî÷êè äî îòðåçêà = ',h:0:6);
  readln;
end.

uses math;
 
type point = record
    x, y :int64;
end;
 
var 
    a, b, c :point;
    d :extended;
 
function mv(p1, p2 :point) :point;
var p3 :point;
begin
    p3.x := p2.x - p1.x;
    p3.y := p2.y - p1.y;
    mv := p3;
end;
 
function dist(p :point) :extended;
begin
    dist := sqrt(sqr(p.x) + sqr(p.y));
end;
 
function scal(p1, p2 :point) :longint;
begin
    scal := p1.x * p2.x + p1.y * p2.y;
end;
 
function vect(p1, p2 :point) :longint;
begin
    vect := p1.x * p2.y - p1.y * p2.x;
end;
 
begin
    assign(input, 'distance4.in');
    reset(input);
    assign(output, 'distance4.out');
    rewrite(output);
    read(a.x, a.y);
    read(b.x, b.y);
    read(c.x, c.y);
 
    d := min(dist(mv(a, b)), dist(mv(a, c)));
 
    if (scal(mv(b, a), mv(b, c)) * scal(mv(c, a), mv(c, b)) >= 0) then
        d := min(d, abs(vect(mv(a, b), mv(a, c))) / dist(mv(c, b)));
 
    writeln(d :0 :9);
end.