#include <iostream>
#include <cstdio>
#include <iomanip>
#include <vector>
#include <map>
#include <set>
#include <queue>
#include <bitset>
#include <stack>
#include <utility>
#include <numeric>
#include <algorithm>
#include <functional>
#include <cctype>
#include <complex>
#include <string>
#include <sstream>
#include <fstream>
#include <cassert>
using namespace std;

//common

typedef int  i32;
typedef long long i64,ll;
typedef long double ld;

#define BR "\n"
#define ALL(c) (c).begin(),(c).end()
#define REP(i,n) for(int i=0;i<(int)(n);++i)
#define FOR(i,l,r) for(int i=(int)l;i<(int)(r);++i)
#define EACH(it,o) for(auto it = (o).begin(); it != (o).end(); ++it)
#define IN(l,v,r) ((l)<=(v) && (v)<(r))

//config
//#define NDEBUG
//#define INF 1<<30
//#define EPS 1e-8
//const ll MOD =100000007;

//debug
#ifdef NDEBUG
#define DUMP(x)
#define DUMPLN(x)
#define DEBUG(x)
#define DEBUGLN(x)
#define LINE()
#define LINELN()
#define CHECK(exp,act)
#define STOP(e)
#else
#define DUMP(x)  cerr << #x << " = " << (x)
#define DUMPLN(x)  DUMP(x) <<endl
#define DEBUG(x) DUMP(x) << LINE() << " " << __FILE__
#define DEBUGLN(x) DEBUG(x)<<endl
#define LINE()    cerr<< " (L" << __LINE__ << ")"
#define LINELN()    LINE()<<endl
#define CHECK(exp,act)  if(exp!=act){DUMPLN(exp);DEBUGLN(act);}
#define STOP(e)  CHECK(e,true);if(!(e)) exit(1);
#endif

template<class T> inline string toString(const vector<T>& x) {
	stringstream ss;
	REP(i,x.size()){
		if(i!=0)ss<<" ";
		ss<< x[i];
	}
	return ss.str();
}

template<class T> inline string toString(const vector<vector<T> >& map) {
	stringstream ss;
	REP(i,map.size()){
		if(i!=0)ss<<BR;
		ss<< toString(map[i]);
	}
	return ss.str();
}
template<class K,class V>  string toString(map<K,V>& x) {
	string res;stringstream ss;
	for(auto& p:x)ss<< p.first<<":" << p.second<<" ";
	return ss.str();
}

string BITtoString(int bit){
    stringstream ss;
    while(bit!=0){ss<<(bit%2);bit/=2;}
    string res=ss.str();reverse(ALL(res));
    return res;
}

template<typename T,typename V> inline T pmod(T v,V MOD){
	return (v%MOD+MOD)%MOD;
}
#define nextInt(n) scanf("%d",&n)
#define defInt(n) int n;nextInt(n)
#define nextLong(n) scanf("%lld",&n)
#define defLong(n) ll n;nextLong(n)
#define nextDouble(n) scanf("%lf",&n)

struct UnionFind{
    vector<int> par; // 親
    vector<int> rank; // 木の深さ
    vector<int> ss;//xの属する集合のサイズ
    int size;//集合の個数
    UnionFind(int n){
        REP(i,n) par.push_back(i);
        rank = vector<int>(n);
        ss=vector<int>(n,1);
        size=n;
    }
    int root(int x){
        if(par[x] == x)return x;
        return par[x] = root(par[x]);
    }
    bool same(int x,int y){
        return root(x) == root(y);
    }
    void unite(int x,int y){
        x = root(x);y = root(y);
        if(x==y)return;
        if(rank[x] < rank[y]){
            par[x] = y;
            ss[y]+=ss[x];
        }else{
            par[y] = x;
            ss[x]+=ss[y];
        }
        if(rank[x] == rank[y]) rank[x]++;
        size--;
    }
    int getS(int x){
        return ss[root(x)];
    }
};

int INF=1<<28;
class Main{
	public:

	int N;
	vector<int> ps;
	vector<int> ds;
	void run(){
		// ifstream cin("D2");
//		ofstream cout( "D2.out" );
		
		cin >> N;
		ps=vector<int>(N);REP(i,N) cin >> ps[i];
		UnionFind uf(N);
		REP(i,N)uf.unite(i,max(min(i+ps[i],N-1),0));
		//どれかが0ならセーフ
		vector<int> ms(N,-1);
		REP(i,N)if(ps[i]==0)ms[uf.root(i)]=i;
		ds=vector<int>(N,INF);
		
		priority_queue<pair<int,int>,vector<pair<int,int>>,greater<pair<int,int>>> que;
		ds[0]=0;que.push(make_pair(0,0));
		vector<bool> passed(N);
		while(!que.empty()){
			pair<int,int> v=que.top();que.pop();
			if(passed[v.second])continue;
			passed[v.second]=true;
			for(int d=1;d<=6;d++){
				int nv=v.second+d;
				nv=max(min(nv,N-1),0);
				if(ms[uf.root(nv)]!=-1 && ds[ms[uf.root(nv)]]>ds[v.second]+1){
					ds[ms[uf.root(nv)]]=ds[v.second]+1;
					que.push(make_pair(ds[ms[uf.root(nv)]],ms[uf.root(nv)]));
				}
			}
		}

		cout << ds[N-1]<<endl;
	}


};
int main(){
	cout <<fixed<<setprecision(15);	
	ios::sync_with_stdio(false);
	Main().run();
	return 0;
}

Measured memory_bytes: 3532