#include<iostream>

#include<cstdio>

#include<cstring>

#include<algorithm>

#define N 1000010

using namespace std;

int n,a[N],cnt1,cnt2;

int read()

{

    int x=,f=;char c=getchar();

    while(c>''||c<''){if(c=='-')f=-;c=getchar();}

    while(c>=''&&c<=''){x=x*+c-'';c=getchar();}

    return ;

}

int main()

{

    scanf("%d",&n);

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

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

    {

        if(a[i]==)cnt1++;

        if(a[i]==)

        {

            if(cnt1==)

            {

                puts("NO");return ;

            }

            else cnt2++,cnt1--;

        }

        if(a[i]==)

        {

            if(cnt1==||(cnt2==&&cnt1<))

            {

                puts("NO");

                return ;

            }

            if(cnt2) cnt2--,cnt1--;

            else cnt1-=;

        }

    }

    puts("YES");

    return ;

}

/*

贪心

反过来括号匹配。

*/

#include <iostream>

#include <cstdio>

#include <cstring>

#include <algorithm>

#include <cstdlib>

''

using namespace std;

const int maxn = ;

int p = ;

int z[maxn],a[maxn],n,m;

int main()

{

    scanf("%d",&n);

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

        scanf("%d",&a[i]);

    scanf("%d",&m);

    int x;

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

    {

        scanf("%d",&x);

        if (a[x]>) a[x] = -a[x];

    }

    for (int x = n; x>=; x--)

    {

        if (a[x]>)

        {

            if (z[p] == -a[x]) p--;

            else

            {

                a[x] = -a[x];

                p++;

                z[p]= a[x];

            }

        }

        else

        {

            p++;z[p]=a[x];

        }

    }

    if (p==)

    {

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

        {

            if (a[i]>) printf("+%d ",a[i]);

            else printf("%d ",a[i]);

        }

    }

    else printf("NO\n");

    return ;

}

/*

Floyed

F[i][j][k]表示从i到j能否以k的方式到达。

K = 括号完全匹配  或者 缺少一个右括号

*/

#include <iostream>

#include <cstdio>

#include <cstring>

#include <algorithm>

#include <cstdlib>

using namespace std;

int n,m;

int g[][][],q[**][],t,x,y,z;

int main()

{

    freopen("maze.in","r",stdin);

    freopen("maze.out","w",stdout);

    scanf("%d%d",&n,&m);

    memset(g,,sizeof(g));

    t = ;

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

    {

        scanf("%d%d%d",&x,&y,&z);

        if (z!=)

        {

            if (z<) z = abs(z);

            else z+=;

            g[x][y][z] = ;

            g[y][x][z] = ;

        }

        else

        {

            g[x][y][z] = ;

            g[y][x][z] = ;

            t++;

            q[t][] = x;

            q[t][] = y;

            q[t][] = ;

            t++;

            q[t][] = y;

            q[t][] = x;

            q[t][] = ;

        }

    }

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

    {

        g[i][i][] = ;

        t++;

        q[t][] = i;

        q[t][] = i;

        q[t][] = ;

    }

    for (int s = ; s<=t; s++)

    {

        int x = q[s][];

        int y = q[s][];

        int status = q[s][];

        if (status!=)

        {

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

                if (g[i][x][status-] == )

                {

                    if (g[i][y][] ==)

                    {

                        g[i][y][] = ;

                        t++;

                        q[t][] = i;

                        q[t][] = y;

                        q[t][] = ;

                    }

                }

        }

        else

        {

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

            {

                if (g[i][x][] == && g[i][y][] == )

                {

                    g[i][y][] =;

                    t++;

                    q[t][]= i;

                    q[t][] = y;

                    q[t][]= ;

                }

                if (g[y][i][] ==  && g[x][i][] ==)

                {

                    g[x][i][] = ;

                    t++;

                    q[t][] = x;

                    q[t][] = i;

                    q[t][]= ;

                }

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

                {

                    if (g[y][i][j] ==  && g[x][i][j+] == )

                    {

                        g[x][i][j+] = ;

                        t++;

                        q[t][] = x;

                        q[t][] = i;

                        q[t][] = j+;

                    }

                }

            }

        }

    }

    int tt = ;

    scanf("%d",&tt);

    for (; tt; tt--)

    {

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

        if (g[x][y][] ==) printf("YES\n");

        else printf("NO\n");

    }

}