import std;

void main () {
    string S = readln.chomp.dup.reverse.idup;
    int acc = 0;
    const int N = S.length.to!int;
    long ans = 0;
    foreach (ref i; 0 .. N) {
        if (S[i] == '0') acc++;
        if (i + 1 < N && S[i] == '1' && S[i + 1] == '1') {
            ans += acc;
            i++;
        }
    }

    writeln(ans);
}

void read (T...) (string S, ref T args) {
    import std.conv : to;
    import std.array : split;
    auto buf = S.split;
    foreach (i, ref arg; args) {
        arg = buf[i].to!(typeof(arg));
    }
}