#include<bits/stdc++.h>

using namespace std;

int n,a[],dp[][] = {};

int main()

{

    ios::sync_with_stdio();

    cin >> n;

    for(int i = ;i <= n;i++)   cin >> a[i];

    int ans = ;

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

    {

        if(a[i] == )

        {

            dp[i][] = dp[i-][]+;

            dp[i][] = dp[i-][];

        }

        else

        {

            dp[i][] = dp[i-][];

            dp[i][] = max(dp[i-][],dp[i-][])+;

        }

    }

    cout << max(dp[n][],dp[n][]) << endl;

    return ;

}

#include<bits/stdc++.h>

using namespace std;

int n,m,k,a[];

int main()

{

    ios::sync_with_stdio();

    cin >> n >> k >> m;

    int sum = ;

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

    {

        cin >> a[i];

        sum += a[i];

    }

    sort(a+,a++k);

    int ans = ;

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

    {

        int cnt = n-i,left = m-sum*i,now = (k+)*i;

        if(left < )    break;

        for(int j = ;j <= k;j++)

        {

            if(left < a[j]*cnt)

            {

                now += min(cnt,left/a[j]);

                break;

            }

            now += cnt;

            left -= a[j]*cnt;

        }

        ans = max(ans,now);

    }

    cout << ans << endl;

    return ;

}

#include<bits/stdc++.h>

using namespace std;

int n,l[],r[];

long long a[],sum[] = {},lm[],rm[];

long long f(int l,int r)

{

    long long t1 = r == ?:sum[r-];

    long long t2 = l == ?:sum[l-];

    return t1-t2;

}

int main()

{

    ios::sync_with_stdio();

    cin >> n;

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

    {

        cin >> a[i];

        sum[i] = sum[i-]+a[i];

    }

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

    {

        int t;

        long long maxx = -1e18;

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

        {

            if(f(,j)-f(j,i) > maxx)

            {

                maxx = f(,j)-f(j,i);

                t = j;

            }

        }

        l[i] = t;

        lm[i] = maxx;

        maxx = -1e18;

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

        {

            if(f(i,j)-f(j,n) > maxx)

            {

                maxx = f(i,j)-f(j,n);

                t = j;

            }

        }

        r[i] = t;

        rm[i] = maxx;

    }

    long long maxx = -1e18;

    int ans1,ans2,ans3;

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

    {

        if(lm[i]+rm[i] > maxx)

        {

            maxx = lm[i]+rm[i];

            ans1 = l[i];

            ans2 = i;

            ans3 = r[i];

        }

    }

    cout << ans1 << " " << ans2 << " " << ans3 << endl;

    return ;

}

#include<bits/stdc++.h>

using namespace std;

int n,m,k,q,mp[][];

struct xx

{

    int x,y,t;

    friend bool operator<(xx a,xx b)

    {

        return a.t < b.t;

    }

}a[];

bool ok(int t)

{

    memset(mp,,sizeof(mp));

    for(int i = ;i <= q && a[i].t <= t;i++)  mp[a[i].x][a[i].y] = ;

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

    {

        for(int j = ;j <= m;j++)   mp[i][j] += mp[i][j-]+mp[i-][j]-mp[i-][j-];

    }

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

    {

        for(int j = ;j <= m-k+;j++)

        {

            int endx = i+k-,endy = j+k-;

            if(mp[endx][endy]-mp[i-][endy]-mp[endx][j-]+mp[i-][j-] == k*k)  return ;

        }

    }

    return ;

}

int main()

{

    ios::sync_with_stdio();

    cin >> n >> m >> k >> q;

    for(int i = ;i <= q;i++)   cin >> a[i].x >> a[i].y >> a[i].t;

    sort(a+,a++q);

    int l = ,r = 1e9+;

    while(l < r)

    {

        int mid = (l+r)/;

        if(ok(mid)) r = mid;

        else    l = mid+;

    }

    if(l == 1e9+)  cout << - << endl;

    else    cout << l << endl;

    return ;

}

#include<bits/stdc++.h>

using namespace std;

int n,ok = ;

long long a[],b[];

struct xx

{

    int to,k;

    xx(int a,int b):to(a),k(b){};

};

vector<xx> v[];

void dfs(int now)

{

    for(int i = ;i < v[now].size();i++)

    {

        int t = v[now][i].to,k = v[now][i].k;

        dfs(t);

        if(a[t] < )

        {

            if(1.0*a[t]*k+a[now] < -1e17)   ok = ;

            a[now] += a[t]*k;

        }

        else    a[now] += a[t];

    }

}

int main()

{

    ios::sync_with_stdio();

    cin >> n;

    for(int i = ;i <= n;i++)   cin >> a[i];

    for(int i = ;i <= n;i++)   cin >> b[i],a[i] -= b[i];

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

    {

        int x,y;

        cin >> x >> y;

        v[x].push_back(xx(i,y));

    }

    dfs();

    if(ok && a[] >= ) cout << "YES" << endl;

    else    cout << "NO" << endl;

    return ;

}

#include<bits/stdc++.h>

using namespace std;

int n,a[],la[] = {};

int main()

{

    ios::sync_with_stdio();

    cin >> n;

    for(int i = ;i <= n;i++)   cin >> a[i];

    long long ans = ;

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

    {

        long long t1 = i-la[a[i]],t2 = n-i+;

        ans += t1*t2;

        la[a[i]] = i;

    }

    ans *= ;

    ans -= n;

    cout << fixed << setprecision() << 1.0*ans/n/n << endl;

    return ;

}