#include <bits/stdc++.h>

using namespace std;
typedef long long int ll ; 

int my(int k,int r,int g){
    
    return min(k,max(r,g));
}


int main() {
    int n ; 
    cin>>n ; 
    int b[n+1] = {0};
    
    int i = 1 ;
    while(i<=n){
        cin>>b[i] ; 
        i++;
    }
    
    int dp[n+1][5]; 
    
    dp[1][2] = b[1] ; 
    dp[1][1] = 100000000 ; 
    dp[2][2] = 100000000 ; 
    dp[2][1] = dp[1][2] + b[2] + b[3] ;
    
    
    i = 3 ; 
    while(i<=n-1){
        
        
        dp[i][2] = b[i] + min(dp[i-2][1],dp[i-2][2]);
        dp[i][1] = b[i] + b[i+1] + dp[i-1][2] ; 
        
        i++;
    }
    dp[i][2] = b[n] + min(dp[i-2][2],dp[i-2][1]);
    dp[i][1] = 100000000 ; 
    cout<<my(dp[n][2],dp[n-1][2],dp[n-1][1]);
    
    
    
    return 0 ; 
}