n = int(input())
ls = [0]*(n+5)
for i in range(n):
    a,b = map(int,input().split())
    ls[i] = [a,b]

dp = [0]*(n+5)

for i in range(n-1,-1,-1):
    dp[i] = dp[i+1]
    c = i + ls[i][1]+1
    dp[i] = max(dp[i],ls[i][0]+(dp[c] if c<n else 0 ))

print(max(dp))