#region Header
#!/usr/bin/env python3
# from typing import *

import sys
import io
import math
import collections
import decimal
import itertools
from queue import PriorityQueue
import bisect
import heapq

def input():
    return sys.stdin.readline()[:-1]

sys.setrecursionlimit(1000000)
#endregion

# _INPUT = """# paste here...
# """
# sys.stdin = io.StringIO(_INPUT)

MOD = 1000000007

def main():
    N = int(input())
    A = list(map(int, input().split()))

    dp = [0 for _ in range(N)]
    dp[0] = 1
    for i in range(N-1):
        j = i + A[i]
        while j < N:
            dp[j] += dp[i]
            j += A[i]
        if A[i] != 1:
            dp[i+1] += dp[i]

    print(dp[N-1])

if __name__ == '__main__':
    main()