[Dignity]

Something like this;

pawn Код:

new bool: crouching[MAX_PLAYERS];

public OnPlayerKeyStateChange(playerid, newkeys, oldkeys)
{
    if(newkeys & KEY_CROUCH)
    {
        crouching[playerid] = true;
    }

    if(newkeys & KEY_SPRINT) || (newkeys & KEY_CROUCH) && (newkeys & KEY_FIRE))
    {
        if(crouching[playerid])
        {
            crouching[playerid] = false;
        }
    }

    return 1;
}

If anyone else knows a more efficient way, please reply.