#include <cstdio> #include <iostream> #include <fstream> #include <vector> #include <list> #include <map> #include <set> #include <queue> #include <stack> #include <bitset> #include <algorithm> #include <sstream> #include <iomanip> #include <cmath> #include <cstdlib> #include <ctype.h> #include <cstring> #include <string> #include <ctime> #include <cassert> #include <utility> using namespace std; int n; string v; int main() { // freopen("date.in", "r", stdin); // freopen("date.out","w", stdout); cin >> n; int cnt = 0; v = ""; char c = ' '; while(cnt < n) { cin >> c; v += c; cnt++; } int res = 0; for(int i = 1; i < n; i++) { if(v[i] == v[i - 1] && v[i - 1] == '1') { res++; v[i] = 0; } } cout << res << endl; return 0; }