N, M = map(int, input().split())
CD = [list(map(int, input().split())) for _ in range(N)]
dp = [[[0] * 11 for _ in range(M + 1)] for _ in range(N + 1)]
CD.sort(reverse=True)
Pot = [2 ** i for i in range(11)]
add = 0
# print(CD)
for i in range(N):
    if(CD[i][0] == 0):
        add += CD[i][1]
    else:
        for j in range(M + 1):
            for k in range(11):
                dp[i + 1][j][k] = max(dp[i + 1][j][k], dp[i][j][k])
                if(j + CD[i][0] * Pot[k] <= M):
                    dp[i + 1][j + CD[i][0] * Pot[k]][k + 1] = max(dp[i + 1][j + CD[i][0] * Pot[k]][k + 1], dp[i][j][k] + CD[i][1])

ans = 0
# for i in range(N + 1):
#     print(i)
#     for j in range(M + 1):
#         print(dp[i][j])
for i in range(M + 1):
    for j in range(11):
        ans = max(ans, dp[N][i][j])
print(ans + add)