@@ -0,0 +1,15 @@
+a = list(map(int, input().strip().split()))
+k = int(input())
+left, right, flag = 0, len(a) - 1, False
+while left <= right:
+ mid = (left + right) // 2
+ if k == a[mid]:
+ print(mid)
+ flag = True
+ break
+ elif k < a[mid]:
+ right = mid - 1
+ else:
+ left = mid + 1
+if not flag:
+ print('Not exist!')
