N,a,b,K=map(int,input().split())
A=list(map(int,input().split()))
x=min(A)
result=10**10
a-=1
b-=1
if A[a]+A[b]<=K:
  result=1
if x+A[b]<=K:
  result=min(result,2)
if result>10:
  result=-1
print(result)