uses crt;
var a,i:integer;
s:real;
begin
clrscr;
write('Nhap a='); readln(a);
s:=0;
for i:=1 to 50 do
s:=s+i/(a+i);
writeln(s:4:2);
readln;
end.
Program HOC24;
var s: real;
i,a: integer;
begin
write('Nhap a = '); readln(a);
s:=0;
if a>2 then
for i:=1 to 50 do s:=s+i/(a+i) else write(a,' chua thoa man dieu kien >2');
write('S = ',S:1:2);
readln
end.