Bai1:

uses crt;
var n,x:longint; t:REAL;
begin
clrscr;
   write('n=');readln(n);
   while t<=n do
      begin
         inc(x);
         t:=t+x/(x+1);
      end;
      writeln(x-1);
readln
end.

Bai 2:

uses crt;
var n,i,max:longint; s:string; a:array[1..100000]of string;
begin
clrscr;
   write('s=');readln(s); n:=1;
   for i:=1 to length(s) do
      if (s[i]=' ')and(i<>1)and(s[i-1]<>' ') then inc(n) else
      if s[i]<>' ' then a[n]:=a[n]+s[i];
   if a[n]='' then dec(n);
   writeln('Xau co ',n,' tu');
   for i:=1 to n do if length(a[i])>max then max:=length(a[i]);
   writeln('Tu dai nhat co ',max,' ky tu');
   writeln('Cac tu dai nhat la: ');
   for i:=1 to n do if length(a[i])=max then write(a[i],' ');
readln
end.

Day so:

uses crt;
var n,i,j,m,t,k:longint;
begin
clrscr;
   write('i,j=');readln(i,j);    k:=1;
   repeat
      inc(n);
      if (n>=i)and(n<=j) then inc(t,k);
      inc(m);
      if m=k then begin inc(k); m:=0; end;
   until n=j;
   writeln(t);
readln
end.