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#include <cstdio>
#include <algorithm>

using i64 = long long;

const int N = 5e5 + 10, inf = 1e9;

i64 s[N], xs[N];
int dp[N], u[N];
int n, m;

void add(int x, int v) {
  for (; x <= m; x += ~x & x + 1) {
    u[x] = std::min(u[x], v);
  }
}

int get(int x, int r = inf) {
  for (; x >= 0; x -= ~x & x + 1) {
    r = std::min(r, u[x]);
  }
  return r;
}

int main() {
  scanf("%d", &n);
  for (int i = 1; i <= n; ++i) {
    scanf("%lld", &s[i]);
    s[i] += s[i - 1];
  }
  for (int i = 0; i <= n; ++i) xs[i] = s[i];
  std::sort(xs, xs + n + 1);
  m = std::unique(xs, xs + n + 1) - xs;
  for (int i = 0; i <= m; ++i) u[i] = inf;
  for (int i = 0; i <= n; ++i) dp[i] = inf;
  int p = std::lower_bound(xs, xs + m, 0) - xs;
  dp[0] = 0;
  add(p, dp[0] - 1);
  for (int i = 1; i <= n; ++i) {
    if (s[i] >= s[i - 1] && dp[i - 1] != inf) dp[i] = dp[i - 1];
    p = std::lower_bound(xs, xs + m, s[i]) - xs;
    dp[i] = std::min(dp[i], get(p) + i);
    add(p, dp[i] - (i + 1));
  }
  if (dp[n] == inf) puts("-1");
  else printf("%d\n", dp[n]);
  return 0;
}