n, V, c = map(int, input().split())
dp = [n * c] * (V + 1)
for _ in range(n):
    v, w = map(int, input().split())
    ndp = [0] * (V + 1)
    for i in range(V + 1):
        ndp[i] = dp[i] - c
        if i >= v:
            ndp[i] = max(ndp[i], dp[i - v] + w, ndp[i - v] + w)
    dp = ndp
    
print(dp[-1])