N,new,p = map(int,input().split())
try:
L = sorted(list(map(int,input().split())),reverse=True)
except:
L = []
k = 0
for i in range(len(L)):
if L[i] <= new:
k = i+1
break
else:
k = N+1
if k > p or (N>=p and L[p-1] >= new):
print(-1)
else:
print(k)