#include<iostream>

#include<cstdio>

#include<cmath>

#include<cstdlib>

#include<cstring>

#include<algorithm>

using namespace std;

int read()

{

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

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

    while (c>=''&&c<='') x=(x<<)+(x<<)+(c^),c=getchar();

    return x*f;

}

#define N 100010

#define P 998244353

#define K 200

int n,a[N],f[N][K+][],g[N][K+][];//0 there is limit

void inc(int &x,int y){x+=y;if (x>=P) x-=P;}

int main()

{

#ifndef ONLINE_JUDGE

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

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

#endif

    n=read();

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

    f[][][]=;

    for (int i=;i<=K;i++) g[][i][]=;

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

    {

    if (a[i]!=-)

    {

        inc(f[i][a[i]][],(g[i-][K][]-g[i-][a[i]-][]+P)%P);

        inc(f[i][a[i]][],f[i-][a[i]][]);

        inc(f[i][a[i]][],g[i-][a[i]-][]),inc(f[i][a[i]][],g[i-][a[i]-][]);

    }

    else

    {

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

        {

            inc(f[i][j][],(g[i-][K][]-g[i-][j-][]+P)%P);

            inc(f[i][j][],f[i-][j][]);

            inc(f[i][j][],g[i-][j-][]),inc(f[i][j][],g[i-][j-][]);

        }

    }

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

    g[i][j][]=(f[i][j][]+g[i][j-][])%P,g[i][j][]=(f[i][j][]+g[i][j-][])%P;

    }

    if (a[n]!=-) cout<<f[n][a[n]][];

    else

    {

        int ans=;

        for (int i=;i<=;i++) inc(ans,f[n][i][]);

        cout<<ans;

    }

    return ;

}

#include<iostream>

#include<cstdio>

#include<cmath>

#include<cstdlib>

#include<cstring>

#include<algorithm>

using namespace std;

int read()

{

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

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

    while (c>=''&&c<='') x=(x<<)+(x<<)+(c^),c=getchar();

    return x*f;

}

#define N 100010

int n,m,p[N],deep[N],fa[N],t=,root;

struct data{int to,nxt;

}edge[N<<];

void addedge(int x,int y){t++;edge[t].to=y,edge[t].nxt=p[x],p[x]=t;}

void dfs(int k)

{

    for (int i=p[k];i;i=edge[i].nxt)

    if (edge[i].to!=fa[k])

    {

        deep[edge[i].to]=deep[k]+;

        fa[edge[i].to]=k;

        dfs(edge[i].to);

    }

}

bool check(int k)

{

    bool flag=;

    int x=;

    for (int i=p[k];i;i=edge[i].nxt)

    if (edge[i].to!=fa[k]) x++;

    if (x==) return deep[k]==m;

    if (x>=)

    {

        for (int i=p[k];i;i=edge[i].nxt)

        if (edge[i].to!=fa[k]) flag=flag&&check(edge[i].to);

    }

    else flag=;

    return flag;

}

int main()

{

#ifndef ONLINE_JUDGE

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

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

#endif

    n=read(),m=read();

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

    {

        int x=read(),y=read();

        addedge(x,y),addedge(y,x);

    }

    dfs();

    for (int i=;i<=n;i++) if (deep[i]>=deep[root]) root=i;

    memset(deep,,sizeof(deep));

    memset(fa,,sizeof(fa));

    dfs(root);

    for (int i=;i<=n;i++) if (deep[i]>=deep[root]) root=i;

    if (deep[root]!=m*) {cout<<"No";return ;}

    for (int i=;i<=m;i++) root=fa[root];

    memset(deep,,sizeof(deep));

    memset(fa,,sizeof(fa));

    dfs(root);

    if (check(root)) cout<<"Yes";

    else cout<<"No";

    return ;

}