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//--------------CHECKPOINT ADD TEST--------------------------

	if(strcmp(cmd, "/check", true) == 0) {

	new Float:x,Float:y,Float:z;
	new Float:xMAX,Float:xMIN,Float:yMAX,Float:yMIN;

	GetPlayerPos(playerid,x,y,z);

	if(IsPlayerConnected(playerid)) {
	xMAX = (x + 30.0); // Co-ordinates are floats. So you should add a float to them.
	xMIN = (x - 30.0);
	yMAX = (y + 30.0);
	yMIN = (y - 30.0);
	checkPoints++;
	checkpoints[checkPoints][0] = x;
	checkpoints[checkPoints][1] = y;
	checkpoints[checkPoints][2] = z;

	checkCoords[checkPoints][0] = xMAX;
	checkCoords[checkPoints][1] = xMIN;
	checkCoords[checkPoints][2] = yMAX;
	checkCoords[checkPoints][3] = yMIN;
	SendClientMessage(playerid,COLOR_WHITE,"NEw CHeckPOint");
	{
		SetTimer("checkpointUpdate",1000,0);
		return 1;
	}
}



//CHECKPOINT UPDATE FUNCTIONS

...