function quitRe(a){         if(a.length===1) return a;         let start=0,end=1;         while(end<a.length){           if(a[end]===a[start]){             end++           }else{             if(end-start>1){               a = a.replace(a.slice(start,end),'')               a = quitRe(a)             }else{               start++               end++             }           }         }         return a;       }