var i,n,s:nteger;
BEGIN
read(n);
for i := 1 to n do
if i mod 2 = 0 then s:= s-1/i;
else s:= s+1/i;
writeln(s);
END.
var i,n,s:nteger;
BEGIN
read(n);
for i := 1 to n do
if i mod 2 = 0 then s:= s-1/i;
else s:= s+1/i;
writeln(s);
END.