Pasted

// https://rathena.org/board/topic/113648-unique-exchanger/
  prontera,155,181,5	script	Sample	4_F_KAFRA1,{
 	OnTalk:
		mes "Select an item to exchange.";
		.@item_1 = select(.menu$) - 1;
		if (!countitem(.item_id[.@item_1])) {
			mes "You dont have "+getitemname(.item_id[.@item_1])+".";
		}
		else {
			for (.@i = 0; .@i < .item_id_size; .@i++) {
				if (.item_id[.@item_1] != .item_id[.@i])
					.@menu$ = .@menu$ + getitemname(.item_id[.@i]);
				.@menu$ = .@menu$ + ":";
			}
			.@item_2 = select(.@menu$) - 1;
			delitem .item_id[.@item_1],1;
			getitem .item_id[.@item_2],1;
		}
		close;
 	OnInit:
		// how long the npc will show
		.second = 3600;
		// list of item that can be exchange
		setarray .item_id, 
			501, 
			502, 
			503, 
			504;
 		.item_id_size = getarraysize(.item_id);
		for (.@i = 0; .@i < .item_id_size; .@i++)
			.menu$ = .menu$ + getitemname(.item_id[.@i) + ":";
		.npc_name$ = strnpcinfo(3);
		end;
 	OnMon0000:	// show on Mon 1200AM
	OnWed1200:	// show on Mon 1200PM
	OnFri1800:	// show on Mon 1600PM
		hideoffnpc .npc_name$;
		announce "Hi...", bc_all;
		sleep (.second * 1000);
		hideonnpc .npc_name$;
		announce "Bye Bye...", bc_all;
		end;
}