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#include <bits/stdc++.h>
using namespace std;
#define rep(i,a,n) for (int i=a;i<n;i++)
#define per(i,a,n) for (int i=n-1;i>=a;i--)
#define pb push_back
#define mp make_pair
#define all(x) (x).begin(),(x).end()
#define fi first
#define se second
#define SZ(x) ((int)(x).size())
typedef vector<int> VI;
typedef long long ll;
typedef pair<int,int> PII;
typedef double db;
//mt19937 mrand(random_device{}());
const ll mod=1000000007;
//int rnd(int x) { return mrand() % x;}
ll powmod(ll a,ll b) {ll res=1;a%=mod; assert(b>=0); for(;b;b>>=1){if(b&1)res=res*a%mod;a=a*a%mod;}return res;}
int gcd(int a,int b) { return b?gcd(b,a%b):a;}
// head

const int N=7e5+5;

#define INF 0x3f3f3f3f

template<class T> inline void read(T &x) {
    x=0; int c=getchar(),f=1;
    for (;!isdigit(c);c=getchar()) if (c==45) f=-1;
    for (;isdigit(c);c=getchar()) (x*=10)+=f*(c-'0');
}
int n,a[N],id[N],dp[N],nd[2*N];
pair<ll,int> pref[N];

void push(int p) {
	nd[p+p]=min(nd[p+p],nd[p]);
	nd[p+p+1]=min(nd[p+p+1],nd[p]);
	nd[p]=INF;
}

void build(int p,int l,int r) {
	if (l==r) {
		nd[p]=INF;
		if (pref[l].fi>=0) nd[p]=0;
		return;
	}
	int md=(l+r)>>1;
	build(p+p,l,md);
	build(p+p+1,md+1,r);
	nd[p]=INF;
}

void modify(int p,int l,int r,int tl,int tr,int val) {
	if (l==tl&&tr==r) {
		nd[p]=min(nd[p],val);
		return;
	}
	if (nd[p]!=INF) push(p);
	int md=(l+r)>>1;
	if (tr<=md) modify(p+p,l,md,tl,tr,val);
	else if (tl>md) modify(p+p+1,md+1,r,tl,tr,val);
	else modify(p+p,l,md,tl,md,val),modify(p+p+1,md+1,r,md+1,tr,val);
}

int query(int p,int l,int r,int x) {
	if (l==r) return nd[p];
	if (nd[p]!=INF) push(p);
	int md=(l+r)>>1;
	if (x<=md) return query(p+p,l,md,x);
	return query(p+p+1,md+1,r,x);
}

int main() {
	read(n);
	rep(i,0,n) read(a[i]);
	pref[0]=mp(a[0],0);
	rep(i,1,n) pref[i]=mp(pref[i-1].fi+a[i],i);
	sort(pref,pref+n);
	build(1,0,n-1);
	rep(i,0,n) id[pref[i].se]=i;
	int curMin=INF;
	rep(i,0,n-1) {
		dp[i]=query(1,0,n-1,id[i]);
		if (dp[i]!=INF) dp[i]+=i;
		if (a[i]<0) curMin=INF;
		curMin=min(curMin,dp[i]);
		if (id[i]+1<n&&curMin!=INF) modify(1,0,n-1,id[i]+1,n-1,curMin-i-1);
	}
	dp[n-1]=query(1,0,n-1,id[n-1]);
	if (dp[n-1]==INF) puts("-1");
	else printf("%d\n",n-1+dp[n-1]);
}