uses crt;
var x,e,s,sk,t:real;
k:longint;
begin
clrscr;
write('x=');readln(x);
e:=0.000001;
s:=0;
t:=-x;
sk:=-x;
k:=1;
while abs(s-sk)>e do
begin
s:=sk;
k:=k+1;
t:=-t*x;
sk:=sk+t/k;
end;
write('S=',s:0:8,' toch=',abs(s-sk):0:8);
readln
end.