N,ww = map(int, input().split())

dp = [ [-float("inf")] * (ww+1) for _ in range(N+1) ]
for i in range(ww+1):
    dp[0][i] = 0

V = list()
W = list()

for _ in range(N):
    v,w = map(int, input().split())
    V.append(v)
    W.append(w)

for i in range(N):
    for j in range(ww+1):
        if 0<=j-W[i]<=ww:
            dp[i+1][j] = max(dp[i][j-W[i]]+V[i],dp[i][j]) 
        else:
            dp[i+1][j] = max(dp[i+1][j],dp[i][j])
print(max(dp[N]) if max(dp[N])>0 else -1)