N, P, K = map(int, input().split())
items = []
for _ in range(N):
    T, B = map(int, input().split())
    items.append((T, B))

dp = [[0] * (K+1) for _ in range(N+1)]
dp[0][0] = P

for i in range(N):
    for j in range(K+1):
        dp[i+1][j] = dp[i][j]

    t, b = items[i]
    for j in range(K):
        if t == 1:
            dp[i+1][j+1] = max(dp[i+1][j+1], dp[i][j] + b)
        else:
            dp[i+1][j+1] = max(dp[i+1][j+1], dp[i][j] * 2)

res = dp[N][K]
if res > 10**18:
    print(-1)
else:
    print(res)