apex extra or split the string

Please use below code:-

String a = '111,112,113,114 etc';
String[] lst = a.split(',');
String result1;
String result2;
System.debug('lst.size()== '+lst.size());
for(Integer i = 0; i<lst.size() ; i++){
    if(i < 3){
        if(i == 0){
            result1 =  lst[i]; 
        }
        if(i> 0 && i<3){
            result1 +=  ','+lst[i];
        }
        if( i== 2){
            result2 =  lst[i];
        }
    }else{
        if(i== 3){
            result2 +=  ','+lst[i];
        } 
    }
}
system.debug('result1 '+result1);
system.debug('result2 '+result2);