Please help me in this: I have created a counter field in account and have written the code like this
trigger AccountUpdationCounter on Account (after update) {

for(Account acts:trigger.new){
if(Trigger.isUpdate){
acts.Counter__c=0;
acts.Counter__c=acts.Counter__c+1;
}
update acts;
}
}
Getting below error after updating from UI:Error:Apex trigger AccountUpdationCounter caused an unexpected exception, contact your administrator: AccountUpdationCounter: execution of AfterUpdate caused by: System.FinalException: Record is read-only: Trigger.AccountUpdationCounter: line 4, column 1