int countMaxCross(string& riverMap)
{
    int n = riverMap.length()+1;
    int lArr[riverMap.length()];
    int rArr[riverMap.length()];
    for (int j = 0; j <n; ++j)
    {
        lArr[j] = 0;
        rArr[j] = 0;
    }
    rArr[0]=1;
    int k = 1;
    char currChar;
    while (k <= n)
    {
        currChar = riverMap[k - 1];
        switch (currChar)
        {
            case 'B':
                lArr[k] = lArr[k - 1] + 1;
                rArr[k] = rArr[k - 1] + 1;
                break;
            case 'R':
                lArr[k] = lArr[k - 1];
                rArr[k] = rArr[k - 1] + 1;
                break;
            default://'L'
                lArr[k] = lArr[k - 1] + 1;
                rArr[k] = rArr[k - 1];
                break;
        }
        rArr[k] = (lArr[k] + 1 < rArr[k]) ? (lArr[k] + 1) : rArr[k];
        lArr[k] = (rArr[k] + 1 < lArr[k]) ? (rArr[k] + 1) : lArr[k];
        k++;
    }

    return rArr[n];
}