N,V,C = map(int,input().split())

l = []
from collections import defaultdict
d = defaultdict(list)
for _ in range(N):
    v,w = map(int,input().split())
    d[v].append(w)
dp = [0] * (V + 1)
for v,l in d.items():
    nx = dp.copy()
    l.sort(reverse = True)
    while l and l[-1] + C <= l[0]:
        l.pop()
    for i in range(1,len(l)):
        l[i] += l[i-1]
    for i in range(V + 1):
        for j in range(len(l)):
            if i + (j+1) * v > V:break
            nx[i + (j+1) * v] = max(nx[i + (j+1) * v],dp[i] + C * (j + 1) + l[j])
        for j in range(len(l) + 1,(V - i) // v + 1):
            nx[i + j * v] = max(nx[i + j * v],dp[i] + C * len(l) + l[-1] + l[0] * (j - len(l)))
        
    dp = nx
print(max(dp))