#include <bits/stdc++.h>
using namespace std;
#define ll long long
const int nx=1e5+5, mod=1e9+7;
ll n, k, u, v, dp[nx], dpr[nx], lvl[nx], force[nx], lcnt, res;
vector<int> d[nx];
void dfs(int u, int p)
{
lvl[u]=lvl[p]+1;
for (auto v:d[u]) if (v!=p) dfs(v, u), dp[u]|=!dp[v];
}
void fillforce(int u, int p)
{
int cnt=0;
for (auto v:d[u]) if (v!=p) cnt++;
if (cnt==1)
{
for (auto v:d[u]) if (v!=p) force[v]=1, fillforce(v, u);
return;
}
if ((lvl[u]%2)&&!dp[u]) for (auto v:d[u]) if (v!=p) force[v]=1, fillforce(v, u);
if ((lvl[u]%2)&&dp[u])
{
int cnt=0;
for (auto v:d[u]) if (v!=p&&!dp[v]) cnt++;
if (cnt==1) for (auto v:d[u]) if (v!=p&&!dp[v]) force[v]=1, fillforce(v, u);
}
}
void dfs2(int u, int p)
{
lcnt+=!(dp[u]|dpr[u]);
//cout<<"debug "<<u<<' '<<dp[u]<<' '<<dpr[u]<<'\n';
int cnt=0, tot=0;
for (auto v:d[u]) if (v!=p) tot++;
for (auto v:d[u]) if (v!=p&&dp[v]) cnt++;
//cout<<"tot "<<cnt<<' '<<tot<<'\n';
for (auto v:d[u])
{
if (v==p) continue;
if (!dpr[u]&&(cnt-dp[v])==tot-1) dpr[v]=1;
dfs2(v, u);
}
}
int main()
{
cin.tie(NULL)->sync_with_stdio(false);
cin>>n>>k;
for (int i=1; i<n; i++) cin>>u>>v, d[u].push_back(v), d[v].push_back(u);
dfs(1, 1);
force[1]=1;
fillforce(1, 1);
//for (int i=1; i<=n;i++) cout<<"f "<<i<<' '<<force[i]<<'\n';
dfs2(1, 1);
//cout<<"lcnt "<<lcnt<<'\n';
if (dp[1])
{
for (int i=1 ;i<=n; i++)
{
if (!force[i]) res=(res+n)%mod;
else if (lvl[i]%2) res=(res+n)%mod;
else res=(res+(n-lcnt))%mod;
}
}
else
{
for (int i=1; i<=n ;i++)
{
if (!force[i]) continue;
if (lvl[i]%2) res=(res+lcnt)%mod;
}
}
cout<<res;
}
/*
5 1
1 2
1 3
3 4
3 5
*/
