1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
#include <bits/stdc++.h>

#define FOR(i,a,b) for(int i=(a);i<(b);++i)
#define FORD(i, a, b) for(int i = (a); i >= (b); --i)
#define VAR(v, i) __typeof(i) v=(i)
#define FORE(i, c) for(VAR(i, (c).begin()); i != (c).end(); ++i)
#define all(v) (v).begin(),(v).end()

#define VI vector<int>
#define PII pair<int,int>
#define st first
#define nd second
#define mp make_pair
#define pb push_back
#define lint long long int

#define debug(x) {cerr <<#x <<" = " <<x <<endl; }
#define debug2(x,y) {cerr <<#x <<" = " <<x << ", "<<#y<<" = "<< y <<endl; } 
#define debug3(x,y,z) {cerr <<#x <<" = " <<x << ", "<<#y<<" = "<< y << ", " << #z << " = " << z <<endl; } 
#define debugv(x) {{cerr <<#x <<" = "; FORE(itt, (x)) cerr <<*itt <<", "; cerr <<endl; }}
#define debugt(t,n) {{cerr <<#t <<" = "; FOR(it,0,(n)) cerr <<t[it] <<", "; cerr <<endl; }}

#define make( x) int (x); scanf("%d",&(x));
#define make2( x, y) int (x), (y); scanf("%d%d",&(x),&(y));
#define make3(x, y, z) int (x), (y), (z); scanf("%d%d%d",&(x),&(y),&(z));
#define make4(x, y, z, t) int (x), (y), (z), (t); scanf("%d%d%d%d",&(x),&(y),&(z),&(t));
#define makev(v,n) VI (v); FOR(i,0,(n)) { make(a); (v).pb(a);} 
#define IOS ios_base::sync_with_stdio(0)
#define HEAP priority_queue

#define read( x) scanf("%d",&(x));
#define read2( x, y) scanf("%d%d",&(x),&(y));
#define read3(x, y, z) scanf("%d%d%d",&(x),&(y),&(z));
#define read4(x, y, z, t) scanf("%d%d%d%d",&(x),&(y),&(z),&(t));
#define readv(v,n) FOR(i,0,(n)) { make(a); (v).pb(a);}

using namespace std;

const int max_n = 500005;

int n,m ;
VI g[max_n];
int r1[max_n];
int r2[max_n];
int p[max_n];

lint res = 0;

void dfs1(int v, int par) {
  p[v] = par;
  FORE(j, g[v]) {
    if (*j != par) {
      dfs1(*j, v);  
    }
  }
}

void dfs(int v) {
  if (r1[v] == -1) {
    VI w;
    lint loc = 0;
    FORE(j, g[v]) {
      if (*j != p[v]) {
        dfs(*j);
        w.pb(r1[*j]);
        w.pb(r2[*j]);
        loc -= r2[*j]-r1[*j];
      }
    }
    sort(all(w));
    r1[v] = w[w.size()/2 - 1];
    r2[v] = w[w.size()/2];
    FORE(i,w) {
      loc += max(r1[v]-*i,*i-r1[v]);
    }
    loc = loc/2;
    res += loc;
  }
}


int main(){
  read2(n,m);
  FOR(i,0,n-1) {
    make2(a,b); a--; b--;
    g[a].pb(b);
    g[b].pb(a);
  }
  FOR(i,0,m) {
    make(ar);
    r1[i] = r2[i] = ar;
  }
  if (m==n) {
    printf("%d\n", max(r1[0] - r1[1], r1[1] - r1[0]));
    return 0;
  } 
  FOR (i, m, n) r1[i] = r2[i] = -1;
  FOR (i, 0, n) p[i] = -1;
  dfs1(m,-2);
  dfs(m);
  printf("%lld\n",res);


}