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
#include <iostream>
#include <vector>

using namespace std;

const int N = 1 << 19;

int n;
long long A[N];
vector<int> B;

long long Pref[N];
int Prev[N];
int Dp[N];

void init() {
    cin >> n;
    
    bool negative = 0;
    
    B.push_back(0);
    
    for (int i=1; i<=n; i++) {
        cin >> A[i];
        
        Pref[i] = Pref[i-1] + A[i];
        
        if (A[i] != 0) {
            B.push_back(i);
        }
        
        if (A[i] < 0) {
            negative = 1;
        }
        
        if (negative == 1) {
            Dp[i] = N;
        }
        
        if (A[i-1] != 0) {
            Prev[i] = i - 1;
        } else {
            Prev[i] = Prev[i-1];
        }
    }
}

void solve() {
    int last = -1;
    
    for (int i=1; i<B.size(); i++) {
        if (A[B[i]] < 0) {
            for (int j=1; j<i; j++) {
                if (Pref[B[i]] - Pref[B[j]-1] >= 0) {
                    Dp[B[i]] = min(Dp[B[i]], B[i] - B[j] + Dp[Prev[B[j]]]);
                }
            }
            
            last = i;
        }
        
        if (A[B[i]] > 0 && Dp[B[i]] > 0) {
            for (int j=1; j<=last; j++) {
                if (Pref[B[i]] - Pref[B[j]-1] >= 0) {
                    Dp[B[i]] = min(min(Dp[B[i]], Dp[B[i-1]]), B[i] - B[j] + Dp[Prev[B[j]]]);
                }
            }
        }
    }
    
    /*
    for (int i=0; i<B.size(); i++) {
        cout << Dp[B[i]] << ' ';
    }
    cout << '\n';
    */
    
    int mini = N;
    
    for (int i=B.size()-1; i>=0; i--) {
        mini = min(mini, Dp[B[i]]);
        
        if (A[B[i]] < 0) {
            break;
        }
    }
    
    if (Pref[n] < 0) {
        cout << "-1\n";
    } else {
        cout << mini << '\n';
    }
}

int main() {
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    
    init();
    solve();
    
    return 0;
}