void LCA(int u, int d)
{
p[u] = u;
dist[u] = d;
int k;
visit[u] = true;
for (k = head[u]; k != 0; k = edge[k].next)
{
if (!visit[edge[k].to])
{
LCA(edge[k].to, d + 1);
p[edge[k].to] = u;
}
}
for (k = qhead[qhead_hash.findHash(id_to_name[u])]; k != 0; k = qedge[k].next)
{
std::vector<int>::iterator j, j_first, j_last;
j_first = name_to_id[surnames.findHash(qedge[k].to)].begin();
j_last = name_to_id[surnames.findHash(qedge[k].to)].end();
for (j = j_first; j != j_last; ++j)
{
if (visit[*j])
{
int lca = find(*j);
int query1 = qmap_hash.findHash(make_pair(id_to_name[u], qedge[k].to));
int query2 = qmap_hash.findHash(make_pair(qedge[k].to, id_to_name[u]));
qmap[query1] = max(qmap[query1], dist[u] + dist[*j] - 2 * dist[lca]);
qmap[query2] = max(qmap[query2], dist[u] + dist[*j] - 2 * dist[lca]);
}
}
}
}
int main(int argc, char const *argv[])
{
int n, q, a, b;
char str[10], str2[10];
while(~scanf("%d%d", &n, &q))
{
memset(head, 0, (n+1)*sizeof(int));
memset(dist, 0, (n+1)*sizeof(int));
memset(visit, 0, (n+1)*sizeof(bool));
memset(qhead, 0, sizeof(qhead));
memset(qmap, 0, sizeof(qmap));
surnames.clear();
qhead_hash.clear();
qmap_hash.clear();
for (int i = 0; i < maxn; ++i) id_to_name[i].clear();
for (int i = 0; i < maxn; ++i) name_to_id[i].clear();
for (int i = 0; i < n; ++i)
{
scanf("%s", str);
id_to_name[i+1] = str;
name_to_id[surnames.insert(str)].push_back(i+1);
}
for (int i = 1; i <= n-1; ++i)
{
scanf("%d%d", &a, &b);
edge[i*2-1].to = b;
edge[i*2-1].next = head[a];
head[a] = i*2-1;
edge[i*2].to = a;
edge[i*2].next = head[b];
head[b] = i*2;
}
for (int i = 1; i <= q; ++i)
{
scanf("%s%s", str, str2);
if ((surnames.findHash(str) == -1) || (surnames.findHash(str2) == -1))
{
qq[i].a = qq[i].b = "";
continue;
}
qq[i].a = str;
qq[i].b = str2;
if (qhead_hash.findHash(str) == -1) qhead[qhead_hash.insert(str)] = 0;
if (qhead_hash.findHash(str2) == -1) qhead[qhead_hash.insert(str2)] = 0;
qedge[i*2-1].to = str2;
qedge[i*2-1].next = qhead[qhead_hash.findHash(str)];
qhead[qhead_hash.findHash(str)] = i*2-1;
qedge[i*2].to = str;
qedge[i*2].next = qhead[qhead_hash.findHash(str2)];
qhead[qhead_hash.findHash(str2)] = i*2;
qmap[qmap_hash.insert(make_pair(str, str2))] = -1;
qmap[qmap_hash.insert(make_pair(str2, str))] = -1;
}
LCA(1, 0);
for (int i = 1; i <= q; ++i)
{
if (qq[i].a == "" || qq[i].b == "")
{
printf("-1\n");
}
else
{
printf("%d\n", qmap[qmap_hash.findHash(make_pair(qq[i].a, qq[i].b))] + 1);
}
}
}
return 0;
}