bits sum pairwise

int Solution::cntBits(vector<int> &A) {
    int max=*max_element(A.begin(),A.end());
    int size=A.size();
    const unsigned int M = 1000000007;
    long long int sum=0;
    for(int i=0;i<=log2(max);i++)
    {
       int ones=0;
        int zeros=0;
        for(auto x:A)
        {
            if(x&(1<<i))
                ones++;
            else
                zeros++;

        }
        sum%=M;
        int z=(2*ones*zeros);

        sum+=z;
        sum%=M;
    }
    return (sum)%M;
}