VAR
 i,j,k:Integer;
 Ps:Extended;

function Nfact(n:LongInt):Extended;
VAR
  i:LongInt;
  fact:Extended;
BEGIN
  IF n=0 THEN fact:=1 ELSE
    BEGIN
      fact:=1;
      FOR i:=1 TO n DO
        fact:=fact*i;
    END;
  Nfact:=fact;
END;

Function C(m,n:LongInt):Extended;
begin
 C:=Nfact(m)/(Nfact(n)*Nfact(m-n));
end;

function X2np(X:Extended; n:WORD):Extended;
Var i:WORD;
    Y:Extended;
Begin
  if n=0 then X2np:=1 else
  if n=1 then X2np:=X else
  begin
    Y:=X;
    for i:=2 to n do Y:=Y*X;
    X2np:=Y;
  end;
End;

BEGIN
 Write('The probability for  0 trees to die is ');
 WriteLn(X2np(0.75,50):22:18);
 Ps:=X2np(0.75,50);
 For j:=1 to 3 do
  begin
   If j=3 then k:=49 else k:=j*17;
   For i:=1+(j-1)*17 to k do
    begin
     Write('The probability for ',i:2,' trees to die is ');
     WriteLn(C(50,i)*X2np(0.25,i)*X2np(0.75,(50-i)):22:18);
     Ps:=Ps+C(50,i)*X2np(0.25,i)*X2np(0.75,(50-i));
    end;
   If j<3 then
    begin
     WriteLn('Press "Enter to continue..."');
     ReadLn;
    end;
  end;
 Write('The probability for 50 trees to die is ');
 WriteLn(X2np(0.25,50):22:18);
 Ps:=Ps+X2np(0.25,50);
 WriteLn('P_sum= ',Ps:22:18);
 ReadLn;
END.