#include <algorithm>
#include <cmath>
#include <climits>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <fstream>
#include <iostream>
#include <list>
#include <map>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <vector>
#include <cassert>
#include <functional>

using namespace std;

#define LOG(...) printf(__VA_ARGS__)
//#define LOG(...)
#define FOR(i,a,b) for(int i=(int)(a);i<(int)(b);++i)
#define REP(i,n) for(int i=0;i<(int)(n);++i)
#define ALL(a) (a).begin(),(a).end()
#define RALL(a) (a).rbegin(),(a).rend()
#define EXIST(s,e) ((s).find(e)!=(s).end())
#define SORT(c) sort((c).begin(),(c).end())
#define RSORT(c) sort((c).rbegin(),(c).rend())
#define CLR(a) memset((a), 0 ,sizeof(a))

typedef long long ll;
typedef unsigned long long ull;
typedef vector<bool> vb;
typedef vector<int> vi;
typedef vector<ll> vll;
typedef vector<vb> vvb;
typedef vector<vi> vvi;
typedef vector<vll> vvll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;

const int dx[] = { -1, 0, 1, 0 }; const int dy[] = { 0, 1, 0, -1 };

int main() {
	int n;
	cin >> n;
	vector<int> mass(n);
	REP(i, n)
		cin >> mass[i];
	vector<int> memo(n, 999999);
	memo[0] = 0;
	queue<int> Q;
	Q.push(0);
	set<int> se;
	while (!Q.empty()){
		int q = Q.front(); Q.pop();
		for (int i = 1; i < 7; i++){
			if (q + i >= n)break;
			int q2 = q;
			
			se.insert(q2);
			q2 += i;
			while (1){
				if (!EXIST(se, q2)){
					se.insert(q2);
					if (mass[q2] == 0 && memo[q2]>memo[q] + 1){
						memo[q2] = memo[q] + 1;
						Q.push(q2);
						break;
					}
					else
						q2 += mass[q2];
				}
				else
					break;
			}
		}
	}
	cout << memo[n - 1] << endl;
}