function fmin(a:double, b:double, tol:double):double
// нахождение точки минимума функции fun(x)
// на интервале [a,b] c точностью tol
var c,x,d,fa,fb,fc,fx,fd,dx,ca,fac,fbc;
  tol=abs(tol);
  fa=fun(a); fb=fun(b);
  if fb<fa then
  begin x=b; b=a; a=x; fx=fb; fb=fa; fa=fx end;
ab:
  c=a+(b-a)/2; fc=fun(c);
  if fa<=fc then
  begin
    if abs(c-a)<=tol then begin fmin=a; goto fin end;
    b=c; fb=fc; goto ab;
  end;
abc:
  if (abs(c-a)<=tol) or (abs(c-b)<=tol)
  then begin fmin=c; goto fin end;
  ca=(c-a)/(b-c); fac=fa-fc; fbc=fb-fc;
  dx=((fac-fbc*ca^2)/(2*(fac+fbc*ca)))*(b-c);
  x=c+dx;
  if x<>c then
  begin
    fx=fun(x);
    if fx<fc then
    begin
      d=x+dx; fd=fun(d);
      if fd>fx then
      begin
        a=d;   b=c;   c=x;
        fa=fd; fb=fc; fc=fx;
        goto abc;
      end;
      if sign(c-d)=sign(d-a) and
      ( (3*abs(c-d)>abs(d-a))or(3*abs(d-a)>abs(c-d)) ) then
      begin
        b=c; c=d; fb=fc; fc=fd; goto abc
      end;
      if sign(c-d)=sign(d-b) and
      ( (3*abs(c-d)>abs(d-b))or(3*abs(d-b)>abs(c-d)) ) then
      begin
        a=c; c=d; fa=fc; fc=fd; goto abc
      end;
    end;
  end else
  begin
    x=c+tol;
    if x<>c then
    begin
      fx=fun(x);
      if fx>=fc then
      begin
        d=c-tol; fd=fun(d);
        if fd>fc then begin fmin=c; goto fin end;
      end;
    end;
  end;
  if abs(c-a)>=abs(b-c) then
  begin
    x=a+(c-a)/2; fx=fun(x);
    if fx<=fc then
    begin b=c; c=x; fb=fc; fc=fx end else
    begin a=x; fa=fx end;
    goto abc;
  end;
  x=b+(c-b)/2; fx=fun(x);
  if fx<=fc then
  begin a=c; c=x; fa=fc; fc=fx end else
  begin b=x; fb=fx end;
  goto abc;
fin:
  end;