n, s, k = map(int, input().split())
u = s + k
l = s - k

ans =[]
for i in range(n):
    a = int(input())
    if abs(s - a) <= k:
        ans.append([i+1, a])

ans.sort()
if len(ans) == 0:
    print("unlucky!")
else:
    for i, a in ans:
        print(i)
        break