/**************************************************************

    Problem: 1088

    User: BLADEVIL

    Language: C++

    Result: Accepted

    Time:20 ms

    Memory:1588 kb

****************************************************************/

//By BLADEVIL

#include <cstdio>

#define maxn 10010

using namespace std;

int n;

int w[maxn][];

int main()

{

    scanf("%d",&n);

    int x; scanf("%d",&x);

    if (x==) w[][]++; else

    if (!x) w[][]++; else

        w[][]=w[][]=;

    for (int i=;i<=n;i++)

    {

        scanf("%d",&x);

        if (x==) w[i][]=w[i-][]; else

        if (!x) w[i][]=w[i-][]; else

        if (x==) w[i][]=w[i-][],w[i][]=w[i-][],w[i][]=w[i-][]; else

        if (x==) w[i][]=w[i-][],w[i][]=w[i-][],w[i][]=w[i-][];

    }

    printf("%d\n",w[n][]+w[n][]);

    return ;

}