begin
write('N= ');
readln(n);
i:=2;s:=0;
while i<=n do
begin
s:=s+1/sqr(i);
i:=i+1;
end;
write('s= ',s);
redln
end.
begin
write('N= ');
readln(n);
i:=2;s:=0;
while i<=n do
begin
s:=s+1/sqr(i);
i:=i+1;
end;
write('s= ',s);
redln
end.