#include<bits/stdc++.h>
using namespace std;
int dp[1000100][3];
int a[1000100];
signed main(){
	int n;
	cin>>n;
	for(int i=1;i<=n;++i){
		cin>>a[i];
		for(int j=0;j<=2;++j) dp[i][j]=2e9;
	}
	dp[1][a[1]+1]=0;
	for(int i=2;i<=n;++i){
		if(a[i]==-1){
			dp[i][0]=dp[i-1][0];
			if(a[i-1]==1){
				dp[i][2]=min(min(dp[i-1][0],dp[i-1][1]),dp[i-1][2])+2;
				dp[i][1]=min(dp[i-1][0],dp[i-1][1])+1;
			}
			else{
				dp[i][2]=dp[i-1][2]+2;
				dp[i][1]=2e9;
			}
		}else if(a[i]==0){
			dp[i][0]=dp[i-1][0]+1;
			dp[i][1]=min(dp[i-1][0],dp[i-1][1]); 
			if(a[i-1]==1){
				dp[i][2]=min(min(dp[i-1][0],dp[i-1][1]),dp[i-1][2])+1;
			}
			else{
				dp[i][2]=dp[i-1][2]+1;
			}
		}else{
			dp[i][0]=dp[i-1][0]+2;
			dp[i][2]=min(min(dp[i-1][0],dp[i-1][1]),dp[i-1][2])+1;
			if(a[i-1]==-1){
				dp[i][1]=min(dp[i-1][0],dp[i-1][1])+1;
			}
			else{
				dp[i][1]=dp[i-1][0]+1;
			}
		}
	}int ans=min(dp[n][0],min(dp[n][1],dp[n][2]));
	if(ans==2e9) printf("BRAK\n");
	else cout<<ans<<endl;
	return 0;
}