uses crt;
var n,i,z:integer;
s:real;
begin
write('N -> ');
readln(n);
s:=0;
z:=1;
for i:=1 to n do
begin
s :=s + z*(1+i/10);
z := -z;
end;
writeln('S=',s:0:1);
readln;
end.
uses crt;
var n,i,z:integer;
s:real;
begin
write('N -> ');
readln(n);
s:=0;
z:=1;
for i:=1 to n do
begin
s :=s + z*(1+i/10);
z := -z;
end;
writeln('S=',s:0:1);
readln;
end.