program point;
var
N,R,x,y:integer;
f1,f2:text;
begin
assign(f1,'input.txt');
assign(f2,'output.txt');
reset(f1);
rewrite(f2);
read(f1,R);
for x :=-r to 0 do begin
for y :=-r to -1 do begin
if (x*x+y*y) <= r*r then N:=N+1;
end;
end;
writeln(f2,N*4+1);
close(f2);
close(f1);
readln;
end.