1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
#include <bits/stdc++.h>

using namespace std;

typedef long long ll;
typedef long double ld;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef vector<bool> vb;
typedef vector<int> vi;
typedef vector<vector<int>> vvi;
typedef vector<ll> vl;
typedef vector<vector<ll>> vvl;
#define pb push_back
#define eb emplace_back
#define mp make_pair
#define mt make_tuple
#define st first
#define nd second
#define FOR(__VAR, __START, __END) for(int __VAR=__START; __VAR<=__END; __VAR++)
#define FORB(__VAR, __START, __END) for(int __VAR=__START; __VAR>=__END; __VAR--)
#define FORK(__VAR, __START, __END, __DIFF) for(int __VAR=__START; __VAR<=END; __VAR+=__DIFF)
#define all(__VAR) (__VAR).begin(), (__VAR).end()
#define rall(__VAR) (__VAR).rbegin(), (__VAR).rend()
#define DEBUG(__VAR) cout << #__VAR << ": " << __VAR << endl;

template<typename __T1, typename __T2>
ostream & operator<<(ostream &out, pair<__T1, __T2> &__VAR)
{
	cout << "[" << __VAR.st << ", " << __VAR.nd << "]";
	return out;
}

template<typename __T>
ostream & operator<<(ostream &out, vector<__T> &__VAR)
{
	cout << "[";
	FOR(i, 0, (int)__VAR.size()-2)
		cout << __VAR[i] << ", ";
	if(__VAR.size()>0)
		cout << __VAR[__VAR.size()-1];
	cout << "]" << endl;
	
	return out;
}

const ll INF=1e17;

//dynamiczne min na przedziale

class segmentTree {
private:
	ll treeSize=1;
	vector<ll> v;
	
	ll getMin(ll left, ll right, ll cur, ll p, ll q) {
		if(right<p || q<left)
			return INF;
		if(p<=left && right<=q)
			return v[cur];
		ll mid=(left+right)/2LL;
		return min(getMin(left,mid,2*cur,p,q),getMin(mid+1,right,2*cur+1,p,q));
	}
	
public:
	segmentTree() {}
	segmentTree(ll N) {
		while(treeSize<N)
			treeSize*=2;
		v.resize(2*treeSize, INF);
	}

	ll getMin(ll p, ll q) {
		return getMin(1,treeSize,1,p,q);
	}
	
	void insert(ll pos, ll val) {
		pos+=treeSize-1;
		v[pos]=min(v[pos],val);
		while(pos/=2LL)
			v[pos]=min(v[2*pos],v[2*pos+1]);
	}
};

int main()
{
	ios_base::sync_with_stdio(0);
	cin.tie(0);
	cout.tie(0);

	ll n;
	cin >> n;
	vector<ll> pref(n+1, 0LL), dp(n+1, INF), a(n+1, 0LL);
	dp[0]=0;
	vector<pll> ind(1, {1LL,0});
	for(int i=1; i<=n; i++) {
		cin >> a[i];
		pref[i]=pref[i-1]+a[i];
		ind.pb({pref[i]+1LL,0});
	}
	sort(ind.begin(), ind.end());
	auto last=unique(ind.begin(), ind.end());
	ind.erase(last, ind.end());
	for(ll i=0; i<ind.size(); i++)
		ind[i].nd=i+1LL;
	segmentTree tree(ind.size());
	auto it=lower_bound(ind.begin(), ind.end(), mp(1LL,0LL));
	tree.insert(it->nd, -1LL);
		
	for(ll i=1; i<=n; i++) {
		if(pref[i]<0LL) {
			dp[i]=INF;
			continue;
		}
		if(a[i]>=0LL)
			dp[i]=dp[i-1];
		it=lower_bound(ind.begin(), ind.end(), mp((ll)(pref[i]+1LL), 0LL));
		dp[i]=min(dp[i], tree.getMin(1LL, it->nd)+i);
		tree.insert(it->nd, dp[i]-i-1LL);
		//cout << i << ". " << pref[i] << " : " << (*it) << ": " << dp[i] << endl;
		//cout << i << ". insert: " << it->nd << ": " << dp[i]-i-1LL << endl;
	}
	
	/*for(ll i=1; i<=n; i++) {
		if(dp[i]<INF)
			cout << dp[i] << ' ';
		else
			cout << "INF "; 
	}
	cout << endl;*/
	if(pref[n]>=0LL)
		cout << dp[n] << '\n';
	else
		cout << -1 << '\n';

	return 0;
}