int beautifulBinaryString(string b) {
    int val =0;
    int n = b.size();
    for (int i=2; i< n; i++) {
        if (b.at(i) == '0' and b.at(i-2)=='0' and b.at(i-1)=='1') {
            b.at(i) = '1';
            val++;
        }
    }
    return val;
}