Laravel how to define 3 relationships with one model?

I have a Model which is called Championship. Championship may have 3 judges which are called Main Judge, Main Secretary and Judge Operator.

All of them linked to User Model and stored in the database as user ID.

My relationships looks like this

class Championship extends Model
{
    protected $table = 'championships';

    public function mainJudge()
    {
        return $this->hasOne('App\User', 'id', 'main_judge');
    }

    public function mainSecretary()
    {
        return $this->hasOne('App\User', 'id', 'main_secretary');
    }

    public function judgeOperator()
    {
        return $this->hasOne('App\User', 'id','judge_operator');
    }
}

But I can't undertand how to define inverse relationship in User model

class User extends Authenticatable
{
    public function sex()
    {
        return $this->belongsTo('App\Models\Sex');
    }

    public function player()
    {
        return $this->hasOne('App\Models\Player', 'user_id');
    }

    public function championship()
    {
    ????
    }

via Chebli Mohamed