1 1 2 2
1000000000 1000000000
1
 1 1 1000000000 1000000000
100 1000000000
1
 1 1 10 18
5 6
5
 2 1 1000000000 2000000000
111 999999999
101 999999998
1
 4 13 400 600
13 30
1 19
1 160
1 113
58 73 15 319 194 362 128 157 336 162 77 90 96
 1 15 100 200
283 8
30 58 16 45 80 82 55 95 24 23 86 28 51 47 20
 3 2 300 400
24 68
13 65
15 113
127 177
 1 1 2 1
1 10
1
 4 2 7 15
10 9
4 4
9 3
4 10
1 6
 2 1 1000000000 2000000000
111 1000000000
101 1000000000
5
 2 1 1000000000 2000000000
111 999999998
101 999999998
1
 1 1 1000000000 1000000000
1 1000000000
1

1000000000
 -1
 5
 111
 1
 -1
 -1
 -1
 4
 101
 -1
 -1

import sys
raw_input = sys.stdin.readline
n,k,s,t = map(int,raw_input().split())
cars = []
for i in range(n):
  cars.append(list(map(int,raw_input().split())))
nums = [0]+sorted(list(map(int,raw_input().split())))+[s]
lo = 0
hi = t*2
while lo < hi:
  mid = (lo+hi)/2
  res = 0
  valid = 1
  for i in range(1,k+2):
    if nums[i]-nums[i-1]>mid:
      valid = 0
      break
    lo2 = 0
    hi2 = nums[i]-nums[i-1]
    while lo2<hi2: #binary search for accelerated
      mid2 = (lo2+hi2)/2
      if 2*mid2+(nums[i]-nums[i-1]-mid2) <= mid:
        lo2 = mid2+1
      else:
        hi2 = mid2
    if lo2*2+(nums[i]-nums[i-1]-lo2) > mid:
      lo2 -= 1
    res += lo2+(nums[i]-nums[i-1]-lo2)*2
  if res <= t and valid:
    hi = mid
  else:
    lo = mid+1
if res > t:
  print -1
  sys.exit()
ans = 99999999999
for i in range(n):
  if cars[i][1] >= lo:
    ans = min(ans,cars[i][0])
if ans==99999999999:
  print -1
else:
  print ans

'''
https://codeforces.com/contest/729/problem/C

with g gas, how fast can you traverse m metres of road

a+2b <= g
a+b = m


'''