class Solution {
public:
    int countCollisions(string directions) {
        int ret = directions.size();
        int len = directions.size();
        for (int i = 0; i < len && directions[i] == 'L'; i++)
            ret -= 1;
        for (int i = len - 1; i >= 0 && directions[i] == 'R'; i--)
            ret -= 1;
        for (int i = 0; i < len; i++)
            if (directions[i] == 'S')
                ret -= 1;
        return ret;
    }
};