program v1l10z1 var integer sum real function znak integer begin if mo

program v1l10z1;
var
  k,m,p,x:integer;
  sum:real;

function znak:integer;
  begin
    if (k mod 2)=0 then
      znak:=1
    else
      znak:=-1
  end;

function xstepk:real;
  var
    i,y:integer;
  begin
    y:=x;
    for i:=2 to k do
      y:=y*x;
    xstepk:=y
  end;

function kfakt:integer;
  var
    i,xf:integer;
  begin
    xf:=1;
    for i:=1 to k do
      xf:=xf*i;
    kfakt:=xf
  end;

begin
  sum:=0;
  write ('M='); readln (m);
  write ('P='); readln (p);
  write ('X='); readln (x);
  for k:=m to p do
    sum:=sum+(znak*(xstepk/kfakt));
  writeln (sum:6:8);
  readln
end.