N = int(raw_input())
tuples = []
for _ in xrange(N):
    v, t = map(int, raw_input().split())
    tuples.append((t, v))

dp = [0] * 10001
tuples.sort()
for tup in tuples:
    for n in xrange(tup[0] - 1, -1, -1):
        v = min(dp[n] + tup[1], 10000)
        dp[v] = max(dp[v], dp[n] + tup[1]);

print max(dp)