python3 代码

n, w = map(int, input().split())
p1, p2 = map(int, input().split())
p = p1 + p2

dp = [0] * (w + 1)

for i in range(n):
    e, y = map(int, input().split())
    for j in range(w, y-1, -1):
        if e <= p:
            dp[j] = max(dp[j], dp[j-y]+1)
print(dp[w])