#include <bits/stdc++.h>
using namespace std;
#define xx first
#define yy second
#define endl "\n"
#define pb push_back
#define int long long
#define ll long long
#define lowbit(x) x & (-x)
typedef pair<int, int> pii;
#define LF(x) fixed << setprecision(x)
#define Yshanqian ios::sync_with_stdio(false), cin.tie(0), cout.tie(0);
const int N = 2e5 + 10, M = 1010, inf = 0x3f3f3f3f, mod = 1e9 + 7, P = 13331;
int n;
int a[N];
int dp[N][2][4];
bool st[N];
int cnt, p[N];
void init()
{
    int n = 2e5;
    for (int i = 2; i <= n; i++)
    {
        if (!st[i])
            p[++cnt] = i;
        for (int j = 1; p[j] <= n / i; j++)
        {
            st[i * p[j]] = 1;
            if (i % p[j] == 0)
                break;
        }
    }
}
void solve()
{
    cin >> n;
    for (int i = 1; i <= n; i++)
        cin >> a[i];
    memset(dp, inf, sizeof dp);

    if (a[1] == 1)
    {
        dp[1][1][2] = inf, dp[1][0][2] = 0;
        if (a[1] % 2)
            dp[1][0][0] = inf, dp[1][1][0] = 1, dp[1][0][1] = 0;
        else
            dp[1][0][1] = inf, dp[1][1][1] = 1, dp[1][0][0] = 0;
    }
    else
    {
        dp[1][1][2] = 1, dp[1][0][2] = inf;
        if (a[1] % 2)
            dp[1][0][0] = inf, dp[1][1][0] = 1, dp[1][0][1] = 0;
        else
            dp[1][0][1] = inf, dp[1][1][1] = 1, dp[1][0][0] = 0;
    }

    for (int i = 2; i <= n; i++)
    {
        int x1 = a[i] % 2, x2 = a[i - 1] % 2;
        if (!st[a[i] + a[i - 1]])
            dp[i][0][x1] = min(dp[i][0][x1], dp[i][0][x2]);
        if (a[i] == 1)
        {
            dp[i][0][2] = min(dp[i][0][2], dp[i - 1][0][2]);
            dp[i][0][2] = min(dp[i][0][2], dp[i - 1][1][2]);
            dp[i][0][2] = min(dp[i][0][2], dp[i - 1][0][0]);
            dp[i][0][2] = min(dp[i][0][2], dp[i - 1][1][0]);
        }
        else
        {
            dp[i][1][2] = min(dp[i][1][2], dp[i - 1][0][2] + 1);
            dp[i][1][2] = min(dp[i][1][2], dp[i - 1][1][2] + 1);
            dp[i][1][2] = min(dp[i][1][2], dp[i - 1][0][0] + 1);
            dp[i][1][2] = min(dp[i][1][2], dp[i - 1][1][0] + 1);
        }

        if (x1)
        {
            dp[i][0][1] = min(dp[i][0][1], dp[i - 1][1][0]);
            dp[i][0][1] = min(dp[i][0][1], dp[i - 1][0][0]);

            dp[i][1][0] = min(dp[i][1][0], dp[i - 1][0][1] + 1);
            dp[i][1][0] = min(dp[i][1][0], dp[i - 1][1][1] + 1);

            dp[i][1][1] = min(dp[i][1][1], dp[i - 1][0][0] + 1);
            dp[i][1][1] = min(dp[i][1][1], dp[i - 1][1][0] + 1);
        }
        else
        {

            dp[i][0][0] = min(dp[i][0][0], dp[i - 1][1][1]);
            dp[i][0][0] = min(dp[i][0][0], dp[i - 1][0][1]);

            dp[i][1][0] = min(dp[i][1][0], dp[i - 1][0][1] + 1);
            dp[i][1][0] = min(dp[i][1][0], dp[i - 1][1][1] + 1);

            dp[i][1][1] = min(dp[i][1][1], dp[i - 1][0][0] + 1);
            dp[i][1][1] = min(dp[i][1][1], dp[i - 1][1][0] + 1);
        }
    }

    int ans = inf;
    for (int i = 0; i <= 1; i++)
        for (int j = 0; j <= 2; j++)
            ans = min(ans, dp[n][i][j]);
    cout << ans << endl;
}
signed main()
{
    Yshanqian;
    int T;
    T = 1;
    init();
    // cin >> T;
    for (int cases = 1; cases <= T; ++cases)
    {
        // cout<<"Case #"<<cases<<": ";
        solve();
    }
    return 0;
}