var
n : integer;
e, sum, an : double;
begin
e := 0.001;
n := 1;
an := 1.0 / exp(ln(2) * n) + 1.0 / exp(ln(3) * n);
sum := an;
while (an > e) do
begin
n := n + 1;
an := 1.0 / exp(ln(2) * n) + 1.0 / exp(ln(3) * n);
sum := sum + an;
end;
write('sum = ', sum:2:6);
end.