arr=[10,11,12,13,14,15,16,17,18,19,20]
element=int(input("enter the element"))
flg=0
low=0
upp=len(arr)-1
while(low<upp):
    mid=(upp+low)//2
    if(element>arr[mid]):
            low=mid+1
    elif(element<arr[mid]):
             upp=mid-1
    elif(element==arr[mid]):
            flg=1
            break
if(flg==0):
    print("element not found")
else:
    print("element found")