const e: array [1..3] of real=(0.001, 1e-6, 1e-9);
var x,a,s:real; k,i:integer;
begin
write('x=');readln(x);
for i:=1 to 3 do
begin
k:=0;
s:=0;
a:=1;
while abs(a)>e[i] do begin
 a:=cos((2*k+1)*x)/(2*k+1);
 s:=s+a;
 k:=k+1;
 end;
writeln(i);
write('s=',s);
writeln(i,': число итераций = ',k);
end;
writeln('y=',-0.5*ln(tan(x/2)));
end.