#include<stdio.h>
#include<stdlib.h>
#define dim 16005
using namespace std;

int i,n,x,j,y,a,*mat[dim],viz[dim];
long long best[dim];
long long Max=-99999999;

int sum = 0;

void DF(int x)
{int i;

  viz[x] = 1;

  for(i=1; i<=mat[x][0]; i++)
   if(! viz[mat[x][i]] )
    {
     DF(mat[x][i]);
     if(best[x] + best[mat[x][i]] > best[x])
       {best[x] = best[x] + best[mat[x][i]];
        if(best[x] > Max) Max = best[x];
       }
    }


}




int main()
{
 FILE *f=fopen("asmax.in","r"), *g=fopen("asmax.out","w");

 fscanf(f,"%d",&n);

  for(i=1; i<=n; i++)
 {fscanf(f,"%lld",&best[i]);
  if(best[i] > Max) Max = best[i];
  }



  for(i=1; i<=n; i++)
  {mat[i] = (int *)realloc(mat[i],sizeof(int));
   mat[i][0] = 0;
  }

 for(i=1; i<n; i++)
 {fscanf(f,"%d%d",&x,&y);
  mat[x][0]++;
  a = mat[x][0];
  mat[x] = (int *)realloc(mat[x], (a+1)*sizeof(int) );

  mat[x][a] = y;

  mat[y][0]++;
  a = mat[y][0];
  mat[y] = (int *)realloc(mat[y], (a+1)*sizeof(int) );
  mat[y][a] = x;
 }



 DF(1);

 fprintf(g,"%lld\n",Max);

fclose(f);
fclose(g);
return 0;
}