N = int(input())
T = []
P = []
dp = []
for i in range(N):
a, b = map(int, input().split())
T.append(a)
P.append(b)
dp.append(b)
dp.append(0)
for i in range(N - 1, -1, -1):
if T[i] + i > N:
dp[i] = dp[i + 1]
else:
dp[i] = max(dp[i + 1], P[i] + dp[i + T[i]])
print(dp[0])