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
#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;

const int M = 1<<20;

int64_t tree[20][M];
int64_t INF = -1e18;

void init_tree() {
  for(int i = 0; i < 20; ++i) {
    for(int j = 0; j < M; ++j) {
      tree[i][j] = INF;
    }
  }
}

int64_t get_min_geq_than(int64_t a) {
  int64_t c = 0;
  for(int i = 19; i >= 0; --i) {
    if(tree[i][2*c] >= a) {
      c = c*2;
    } else if(tree[i][c*2+1] >= a) {
      c = c*2+1;
    } else {
      return INF;
    }
  }
  return c-(1<<19);
}

void append(int64_t el, int64_t cost) {
  cost += (1<<19);
  tree[0][cost] = el;
  int64_t c = cost;
  for(int i = 1; i < 20; ++i) {
    c /= 2;
    tree[i][c] = max(tree[i-1][2*c], tree[i-1][2*c+1]);
  }
}

int main() {
  init_tree();
  ios_base::sync_with_stdio(false);
  int n;
  int64_t a;
  cin >> n;


  int64_t currentEl = 0;
  
  append(0, 0);

  for(int i = 0; i < n; ++i) {
    cin >> a;
    int64_t mini = get_min_geq_than(-currentEl);
    if(mini != INF) {
      append(-currentEl, mini-1);
    }
    currentEl += a;
  }
  int64_t result = get_min_geq_than(-currentEl);
  if(result == INF) {
    cout << "-1\n";
  } else {
    cout << result+n << '\n';
  }

}