program andanh;
uses crt;
var tong: real;
n,i:integer;
begin
clrscr; i:= 1; tong:= 1;
write('Nhap N: ');readln(n);
while i <= n do
begin
tong:= tong + 1/(i * (i + 1));
i:= i + 1;
end;
write('Tong la: ',tong:0:2);
readln
end.
uses crt;
var a:real;
n,i:longint;
begin
clrscr;
write('n='); readln(n);
a:=0;
i:=1;
while i<=n do
begin
a:=a+1/(i*(i+1));
inc(i);
end;
writeln(a:4:2);
readln;
end.