var
ch : string;
a, b : array[0..200] of longint;
n, i, t, res : longint;
begin
read(ch);
n := length(ch);
for i := 0 to 199 do
b[i] := 0;
for i := 1 to n do
begin
a[i] := ord(ch[i]) - ord('0');
b[i] := b[i-1] + a[i];
end;
res := b[n];
t := 0;
for i := n downto 1 do
begin
if a[i] = 0 then
inc(t);
if (b[i-1] + t < res) then
res := b[i-1] + t;
end;
writeln(res);
end. 输入：1001101011001101101011110001
输出：1
