#include <algorithm>#include <iostream>#include <vector>#include <string.h>#define ll long long#define MAX 100001using namespace std;int g[MAX];int main(){int n;while (cin >> n){if (n == 0) break;int one = -1, ans = 0;for (int i = 0;i < n;++i){cin >> g[i];if (g[i] == 1)one = i;}if (one == -1) cout << (n + 1) / 2 << endl;else {for (int i = (one + 1) % n;i != one;){int j = i, cnt = 0;while (j != one && g[j] == 0){j = (j + 1) % n;cnt++;}ans += cnt / 2;if (j == one) break;i = (j + 1) % n;}cout << ans << endl;}}return 0;}
