b:
uses crt;
var i,n,s:integer;
begin
clrscr;
readln(n);
s:=0;
for i:=1 to n do s:=s+2*i;
writeln(s);
readln;
end.
c:
uses crt;
var i,n,s:integer;
begin
clrscr;
readln(n);
s:=0;
for i:=1 to n do s:=s+i;
writeln(s);
readln;
end.
d:
uses crt;
var i,n,s:integer;
begin
clrscr;
readln(n);
s:=0;
for i:=0 to n do s:=s+2*i+1;
writeln(s);
readln;
end.