#yukicoder423C Sword

N, P, K = map(int, input().split())
DP = [P] + [0] * K
for _ in range(N):
    t, b = map(int, input().split())
    nDP = [0] * (K + 1)
    for k in range(K + 1):
        if DP[k] == 0: continue
        nDP[k] = max(nDP[k], DP[k])
        if k == K: continue
        if t == 1:
            nDP[k + 1] = max(nDP[k + 1], DP[k] + b)
        if t == 2:
            nDP[k + 1] = max(nDP[k + 1], DP[k] * 2)
    DP, nDP = nDP, DP
    if DP[K] > 10 ** 18:
        exit( print(-1) )
print(DP[K])