Program vct;
Uses crt;
var
A,i,n:integer;
S:=0;
begin
writeln('moi nhap n: '); readln(n);
for i:=1 to n-2 do
begin
S:=S+1/(i*(i+2));
end;
write(S); readln;
end.
progran bai1;
var s,i,n:longint;
begin
write('N= ');
readln(n);
s:=0;
for i:=1 to n do
s:=s+1/i*(i+2);
writeln('Tong la ',s);
readln
end.