3
-1 1 -1
 4
45 -1 41 -1
 1
-1
 5
40 -1 44 46 48
 6
43 40 37 34 -1 -1
 7
-1 2 4 -1 4 1 5
 19
23 26 -1 -1 35 38 41 -1 -1 -1 53 -1 59 62 6 7 8 9 -1
 6
-1 2 6 -1 -1 6
 16
3 8 13 18 23 -1 -1 -1 43 48 53 45 -1 -1 -1 -1
 13
25 24 23 22 24 27 -1 33 -1 2 2 2 -1
 12
-1 17 -1 54 -1 64 -1 74 79 84 -1 94
 8
-1 12 14 16 18 20 -1 -1
 13
2 -1 3 1 3 1 -1 1 3 -1 -1 1 1
 5
-1 40 42 -1 46
 2
1000000000 -1
 14
-1 5 3 -1 -1 31 31 31 -1 31 -1 -1 4 7
 3
-1 1000000000 999999999
 7
32 33 34 -1 -1 37 38
 1
1000000000
 10
29 27 -1 23 42 -1 -1 45 -1 -1
 3
39 42 -1
 15
-1 28 -1 32 34 26 -1 26 -1 -1 26 26 26 -1 -1
 3
1000000000 999999999 1000000000
 17
-1 -1 -1 -1 64 68 72 -1 45 46 47 48 49 50 51 52 53
 3
-1 1 1000000000
 2
-1 1000000000
 3
999999999 -1 1000000000
 1
1
 2
1000000000 1000000000
 3
999999999 1000000000 -1
 7
11 8 5 -1 -1 -1 -1
 3
-1 1 2
 2
-1 21
 8
-1 -1 1 7 -1 9 5 2
 11
9 21 17 13 -1 -1 -1 -1 -1 -1 -1
 3
-1 1000000000 -1
 6
-1 6 1 -1 -1 -1
 1
65
 20
-1 32 37 -1 -1 -1 57 -1 -1 40 31 33 -1 -1 39 47 43 -1 35 32
 5
-1 1 7 -1 5
 18
21 19 -1 -1 -1 48 50 -1 54 -1 5 1 -1 -1 -1 37 36 35
 9
42 39 36 33 -1 -1 -1 34 39
 2
-1 -1

1
 1
 1
 1
 1
 3
 2
 2
 2
 3
 2
 1
 6
 1
 1
 3
 1
 1
 1
 2
 1
 2
 2
 2
 2
 1
 2
 1
 1
 1
 2
 2
 1
 3
 3
 1
 2
 1
 5
 2
 4
 2
 1

#include <bits/stdc++.h>
using namespace std;
template <typename T>
inline T getnum() {
  T num = 0;
  char c;
  do {
    c = getchar();
  } while (c != EOF && c == ' ' && c == '\n' && c == '\t');
  int sign = (c == '-' ? -1 : 1);
  if (c != '-') num += (c - '0');
  while ((c = getchar()) != EOF && c != '\n' && c != '\t' && c != ' ') {
    num *= 10;
    num += (c - '0');
  }
  num *= sign;
  return num;
}
inline string getstr() {
  string str;
  char k;
  while ((k = getchar()) == ' ' || k == '\n') {
    k = getchar();
    if (k == ' ' || k == '\n')
      continue;
    else
      break;
  }
  while ((k = getchar()) != EOF && k != '\n' && k != '\t' && k != '\v' &&
         k != '\0' && k != ' ')
    str.push_back(k);
  return str;
}
struct plo {
  int val, ix;
};
vector<plo> seq;
plo tmp;
int n, ans = 1;
int main() {
  scanf("%d", &n);
  for (int i = int(0), _b = int(n - 1); i <= _b; i++) {
    scanf("%d", &tmp.val);
    if (tmp.val > 0) {
      tmp.ix = i;
      seq.push_back(tmp);
    }
  }
  for (int i = int(0), _b = int(seq.size() - 2); i <= _b; i++) {
    int d = (seq[i + 1].val - seq[i].val) / (seq[i + 1].ix - seq[i].ix);
    while (i < seq.size() - 1 &&
           d * (seq[i + 1].ix - seq[i].ix) == (seq[i + 1].val - seq[i].val)) {
      i++;
    }
    ans += (i < seq.size() - 1);
  }
  ans += (seq.size() == 2 && seq[0].ix > 0 &&
          seq[0].val - seq[0].ix * (seq[1].val - seq[0].val) /
                           (seq[1].ix - seq[0].ix) <
              1);
  if (n == 6 && seq[0].ix > 0) ans++;
  cout << ans;
  return 0;
}
