#include <bits/stdc++.h>   using namespace std;   const int M = 2 * 1e5 + 10;   int a[M];   int main() {     long long s, n, p1, c, pos1, pos2, p2, i, ans = 1, d, x, j;     scanf( %I64d , &n);     for (i = 0; i < n; i++) scanf( %I64d , &a[i]);     if (a[0] != -1) {       p1 = a[0];       pos1 = 0;       c = 1;     } else       c = 0;     s = 0;     ans = 1;     for (i = 1; i < n; i++) {       if (i == 10) i = 10;       if (c == 0) {         if (a[i] != -1) {           c = 1;           p1 = a[i];           pos1 = i;         }         continue;       }       if (c == 1) {         if (a[i] != -1) {           if ((a[i] - p1) % (i - pos1) != 0) {             ans++;             s = i;             c = 1;             p1 = a[i];             pos1 = i;           } else {             c = 2;             p2 = a[i];             pos2 = i;             d = (p2 - p1) / (pos2 - pos1);             x = p1 + d * (s - pos1);             if (x <= 0) {               ans++;               c = 1;               p1 = a[i];               pos1 = i;               s = i;             }           }         }         continue;       }       d = (p2 - p1) / (pos2 - pos1);       x = p1 + d * (i - pos1);       if (a[i] == -1) {         if (x <= 0) {           ans++;           c = 0;           s = i;         }         continue;       } else {         if (x != a[i]) {           ans++;           s = i;           c = 1;           p1 = a[i];           pos1 = i;         }       }     }     printf( %I64d , ans);     return 0;   }   