program arcszekans;
var x,r,si :real;
begin
     Writeln('Kerem a szekans erteket!');
     readln(x);
     si:=sqrt(1-1/(x*x));
     x:=arctan(si/sqrt(1-si*si));
     r:=x*180/pi;
     writeln('A szog: ', r:8:2);
     readln
end.