#include <cstdio>

#include <cstring>

#include <algorithm>

#define N 1000010

using namespace std;

int f[N][],n,a[N];

int min(int a,int b,int c,int d){

    return min(min(a,d),min(b,c));

}

int min(int a,int b,int c){

    return min(a,min(b,c));

}

int calc(int x,int to,int v){

    v--;

    if(x==to) return ;

    if(x+v==to) return ;

    if(x+*v==to) return ;

    return 0x3f3f3f3f;

}

int main(){

    memset(f,0x3f,sizeof(f));

    scanf("%d",&n);

    for(int i=;i<=n;i++) scanf("%d",&a[i]),a[i]++;

    f[][a[]]=;

    for(int i=,s1,s2;i<=n;i++){

        f[i][]=min(f[i][],f[i-][]+calc(a[i],,));

        f[i][]=min(f[i][],f[i-][]+calc(a[i],,),f[i-][]+calc(a[i],,));

        f[i][]=min(f[i][],f[i-][]+calc(a[i],,),f[i-][]+calc(a[i],,),f[i-][]+calc(a[i],,));

    }

    int ans=min(f[n][],f[n][],f[n][]);

    if(ans>=0x3f3f3f3f) puts("BRAK");

    else printf("%d\n",ans);

    return ;

}