import java.io.FileNotFoundException;
import java.util.Arrays;
import java.util.Scanner;

public class Main {
	public static void main(String[] args) throws FileNotFoundException {
		long t = System.currentTimeMillis();
		new Main().run();
		System.err.println(System.currentTimeMillis() - t);
	}
	
	int solve(int l,int r,int[] A) {
		int sum=0;
		for(int i=0;i<A.length;++i)sum+=A[i];
		if((r-l+1)/2*(r-l+1)/2>sum)return Integer.MAX_VALUE/3;
		int ans=0;
		for(int i=0;i<A.length;++i) {
			if(!(l<=i&&i<r)) {
				ans+=A[i];
			}else {
				int need=Math.min(i-l+1, r-i);
				ans+=Math.max(0, A[i]-need);
			}
		}
		return ans;
	}
	
	
	void run() {
		Scanner sc = new Scanner(System.in);
		int N=sc.nextInt();
		int[] A=new int[N];
		for(int i=0;i<N;++i)A[i]=sc.nextInt();
		int ans=Integer.MAX_VALUE/3;
		for(int l=0;l<N;++l) {
			for(int r=l+1;r<=N;r+=2) {
				ans=Math.min(ans,solve(l,r,A));
			}
		}
		System.out.println(ans);
	}


	static void tr(Object... objects) {
		System.out.println(Arrays.deepToString(objects));
	}

}