var a : string;
function BIN_DEC(x:string):longint;
const digits:array [0..1] of char = ('0','1');
var res,ves:longint; i,j:byte;
begin
res:=0; ves:=1;
for i:=length(x) downto 1 do begin
j:=0;
while (digits[j]<>x[i]) do inc(j);
res:=res+ves*j;
ves:=ves*2;
end;
BIN_DEC:=res;
end;
begin { основная программа }
readln( a );
writeln( BIN_DEC(a) );
end.