from sys import stdin,setrecursionlimit#,set_int_max_str_digits
#import pypyjit
#pypyjit.set_param('max_unroll_recursion=-1')
setrecursionlimit(20000000) # これこどふぉだと無理
#set_int_max_str_digits(200010)
mod = 998244353 
ii = lambda :int(stdin.readline())
mi = lambda :map(int,stdin.readline().split())
li = lambda :list(mi())
gmi = lambda :map(lambda x: int(x) - 1, stdin.readline().split())
gi = lambda :list(map(lambda x: 0 if x == "." else 1,input())) # グリッド入力受け取り
py = lambda :print("Yes")
pn = lambda :print("No")
pf = lambda :print("First") 
ps = lambda :print("Second")
vec = [(1,0),(-1,0),(0,-1),(0,1)]
vec1 = [(1,0),(1,1),(0,1),(-1,1),(-1,0),(-1,-1),(0,-1),(1,-1)] #8方向
inf = 2*10**18


n,k = mi() 
tmp = 0 
data = [] 
for _ in range(n):
    c,v = mi() 
    if c == 0:
        tmp += v
        continue
    data.append([c,v]) 

data.sort(reverse=True) 

m = 15
dp = [[0]*(k+1) for _ in range(m)]
p = [1] 
for _ in range(m):
    p.append(p[-1]*2)

for c,v in data:
    ndp = [[0]*(k+1) for _ in range(m)] 
    
    for i in range(m): # 何個使ったか
        nc = c *p[i] 
        for j in range(k+1):
            ndp[i][j] = max(ndp[i][j],dp[i][j]) 
            if i < m and j + nc <= k:
                ndp[i+1][j+nc] = max(ndp[i+1][j+nc],dp[i][j]+v) 

    dp = ndp
    # for i in dp:
    #     print(i)
    # print()

ans = 0 

for i in dp:
    ans = max(ans,max(i))

print(ans+tmp)