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>
#define mp make_pair
#define pb push_back
#define fi first
#define se second
#define pii pair<int,int>
#define ull usigned long long
#define ll long long
#define int long long
using namespace std;
int n;
//Idea! Is! Really! Not! Cheap!
vector<pair<int,int> > a;
bool now[200001];
main(){
    cin>>n;
    for(int i=0;i<n;i++){
        int x;
        cin>>x;
        if(x!=-1)
            a.pb(mp(i,x));
    }
    int cnt=0;
    if(a.size()==0){
        cout<<1<<endl;
        return 0;
    }
    int i=0;
    for(i=0;i<a.size();i++){
        int now1=i+1,now2=i+2;
        cnt++;
        if(now2>a.size())
            break;
        if((a[now2].se>a[now1].se && a[now2-1].se<a[now1-1].se) || (a[now2-1].se>a[now1-1].se && a[now2].se<a[now1].se) 
            || (a[now2].se-a[now1].se)%(a[now2].fi-a[now1].fi)|| a[now2].se-((a[now2].se-a[now1].se)/(a[now2].fi-a[now1].fi)*(a[now2].fi-a[i].fi))<=0){
            i++;
            continue;
        }
        if(i==0 && a[i].se!=0)
            if(a[i].se-a[i].fi*(a[now2].se-a[now1].se)/(a[now2].fi-a[now1].fi)<=0)
                cnt++;
        while(now2<a.size()-1){
            now1++,now2++;
            if((a[now2].se>a[now1].se && a[now2-1].se<a[now1-1].se) || (a[now2-1].se>a[now1-1].se && a[now2].se<a[now1].se) 
            || ((a[now2].se-a[now1].se)%(a[now2].fi-a[now1].fi)|| a[now2].se-((a[now2].se-a[now1].se)/(a[now2].fi-a[now1].fi)*(a[now2].fi-a[now2-2].fi))<=0)){
                now1--,now2--;
                break;
            }
            if((a[now2].se-a[now1].se)/(a[now2].fi-a[now1].fi)!=(a[i+2].se-a[i+1].se)/(a[i+2].fi-a[i+1].fi)){
                now1--,now2--;
                break;
            }
        }
        i=now2;
    }
    if(a.size()==2)
        if((a[1].se-a[0].se)%(a[1].fi-a[0].fi))
            cnt++;
    if(a.size()==2 && a[0].se!=0)
        if(a[0].se-a[0].fi*(a[1].se-a[0].se)/(a[1].fi-a[0].fi)<=0)
            cnt++;
    cout<<cnt<<endl;
    return 0;
}