#include<bits/stdc++.h> 

using namespase std;
int main(){
	freopen("硬币翻转.in","r",stdin);
	freopen("硬币翻转.out","w",stdout);
 
    const int n = 10000;   
    int a[n]; 
	for(int i=0;i<n;i++){
		cin>>a[i];
	} 
    int j = 0; // 记录翻转次数  
    bool b = false; // 是否已翻转 
  
    for (int i = 0; i <n; ++i) {  
        if (a[i] == 0 || b=false) {  
            j++; 
        	b = !b; 
        }  
    }  

    cout << flips << endl;  
  
    return 0;  
}