def chmax(DP,i,v):
    if DP[i] < v: DP[i] = v
def chmin(DP,i,v):
    if DP[i] > v: DP[i] = v

INF = 10**18 + 1
N, P, K = map(int, input().split())
dp = [[-1] * (K + 1) for _ in range(N + 1)]
dp[0][0] = P

for i in range(N):
    t, b = map(int, input().split())
    for j in range(K + 1):
        val = dp[i][j]
        if val == -1:
            continue
        # 不採用
        chmax(dp[i + 1], j, val)
        # 採用
        if j + 1 <= K:
            if t == 1:
                score = val + b
            else:
                score = val * 2
            if score >= INF:
                score = INF
            chmax(dp[i + 1], j + 1, score)

ans = dp[-1][-1]
if ans == INF:
    ans = -1
print(ans)