#include <iostream>#include <cstdio>#include <cstdlib>#include <cmath>#include <algorithm>#include <climits>#include <cstring>#include <string>#include <set>#include <bitset>#include <map>#include <queue>#include <stack>#include <vector>#include <cassert>#include <ctime>#define rep(i,m,n) for(i=m;i<=n;i++)#define mod 1000000007#define inf 0x3f3f3f3f#define vi vector<int>#define pb push_back#define mp make_pair#define fi first#define se second#define ll long long#define pi acos(-1.0)#define pii pair<int,int>#define ls rt<<1#define rs rt<<1|1#define sys system("pause")const int maxn=1e5+10;const int N=1e5+10;using namespace std;ll gcd(ll p,ll q){return q==0?p:gcd(q,p%q);}ll qpow(ll p,ll q){ll f=1;while(q){if(q&1)f=f*p%mod;p=p*p%mod;q>>=1;}return f;}int n,m,k,t,st[maxn],ed[maxn],dep[maxn],fa[20][maxn],bel[maxn],son[maxn],pos[maxn],a[maxn],dfs_cl,mi[maxn<<2];vi e[maxn];void dfs1(int x,int y){    dep[x]=dep[y]+1;    fa[0][x]=y;    son[x]=1;    for(int i=1;fa[i-1][fa[i-1][x]];i++)    {        fa[i][x]=fa[i-1][fa[i-1][x]];    }    for(int i=0;i<e[x].size();i++)    {        int z=e[x][i];        if(z==y)continue;        dfs1(z,x);        son[x]+=son[z];    }}void dfs2(int x,int y,int ch){    int ma=0;    pos[x]=++dfs_cl;    st[x]=dfs_cl;    a[dfs_cl]=x;    bel[x]=ch;    for(int i=0;i<e[x].size();i++)    {        int z=e[x][i];        if(z==y)continue;        if(son[z]>son[ma])ma=z;    }    if(ma!=0)dfs2(ma,x,ch);    for(int i=0;i<e[x].size();i++)    {        int z=e[x][i];        if(z==y||z==ma)continue;        dfs2(z,x,z);    }    ed[x]=dfs_cl;}int lca(int x,int y){    if(dep[x]<dep[y])swap(x,y);    for(int i=19;i>=0;i--)if(dep[fa[i][x]]>=dep[y])x=fa[i][x];    if(x==y)return x;    for(int i=19;i>=0;i--)    {        if(fa[i][x]!=fa[i][y])x=fa[i][x],y=fa[i][y];    }    return fa[0][x];}void pup(int l,int r,int rt){    mi[rt]=min(mi[ls],mi[rs]);}void build(int l,int r,int rt){    if(l==r)    {        mi[rt]=a[l];        return;    }    int mid=l+r>>1;    build(l,mid,ls);    build(mid+1,r,rs);    pup(l,r,rt);}int gao(int L,int R,int l,int r,int rt){    if(L==l&&R==r)return mi[rt];    int mid=l+r>>1;    if(R<=mid)return gao(L,R,l,mid,ls);    else if(L>mid)return gao(L,R,mid+1,r,rs);    else return min(gao(L,mid,l,mid,ls),gao(mid+1,R,mid+1,r,rs));}void upd(vector<int>&a,int x,int y){    while(bel[x]!=bel[y])    {        if(dep[bel[x]]<dep[bel[y]])swap(x,y);        a.pb(pos[x]);        a.pb(pos[bel[x]]);        x=fa[0][bel[x]];    }    if(pos[x]>pos[y])swap(x,y);    a.pb(pos[y]);    a.pb(pos[x]);}int main(){    int i,j;    scanf("%d",&t);    while(t--)    {        scanf("%d%d",&n,&m);        rep(i,1,n)e[i].clear();        rep(i,1,n)rep(j,0,19)fa[j][i]=0;        rep(i,1,n-1)scanf("%d%d",&j,&k),e[j].pb(k),e[k].pb(j);        dfs1(1,0);        dfs_cl=0;        dfs2(1,0,1);        build(1,n,1);        while(m--)        {            int x,y;            scanf("%d%d",&x,&y);            vector<int>tmp;            int lc=lca(x,y);            upd(tmp,x,y);            int s=st[lc],t=ed[lc];            if(lc<1||lc>n)return 0;            sort(tmp.begin(),tmp.end());            int mi=1e9;            for(i=0;i<tmp.size();i+=2)            {                if(s<=tmp[i]-1)mi=min(mi,gao(s,tmp[i]-1,1,n,1));                s=tmp[i+1]+1;            }            if(s<=t)mi=min(mi,gao(s,t,1,n,1));            printf("%d\n",mi==1e9?-1:mi);        }    }    return 0;}