import sys
N = int(sys.stdin.readline())
answer = [0] * (N+2)
array = [[0,0]]
for i in range(N):
array.append(list(map(int,sys.stdin.readline().split())))
array.append([0,0])
maxValue = 0
for i in range(N+1 , 0 , -1):
t = array[i][0]
p = array[i][1]
if(i + t <= N+1):
maxValue = max(answer[i + t] + p, maxValue)
answer[i] = maxValue
print(maxValue)