CF915F

#include<bits/stdc++.h>

using namespace std;

#define gc c=getchar()
#define r(x) read(x)
#define ll long long
#define fi first
#define se second

template<typename T>
inline void read(T&x){
    x=0;T k=1;char gc;
    while(!isdigit(c)){if(c=='-')k=-1;gc;}
    while(isdigit(c)){x=x*10+c-'0';gc;}x*=k;
}

const int N=1e6+7;

struct Edge{
    int u,v,w;
}E[2][N];

inline bool cmp0(const Edge &a,const Edge &b){
    return a.w>b.w;
}

inline bool cmp1(const Edge &a,const Edge &b){
    return a.w<b.w;
}

ll ans[2];
int a[N],siz[N],fa[N];

int find(int x){
    return x==fa[x]?x:fa[x]=find(fa[x]);
}

inline void Union(int u,int v){
    siz[fa[u]]+=siz[fa[v]];
    fa[fa[v]]=fa[u];
}

int main() {
    int n;r(n);
    for(int i=1;i<=n;++i){
        r(a[i]);
    }
    for(int i=1;i<n;++i){
        int u,v;r(u),r(v);
        E[0][i]={u,v,min(a[u],a[v])};
        E[1][i]={u,v,max(a[u],a[v])};
    }
    sort(E[0]+1,E[0]+n,cmp0);
    sort(E[1]+1,E[1]+n,cmp1);
    for(int k=0;k<2;++k){
        for(int i=1;i<=n;++i){
            fa[i]=i;
            siz[i]=1;
        }
        for(int i=1;i<n;++i){
            int u=E[k][i].u;
            int v=E[k][i].v;
            if(find(u)^find(v)){
                ans[k]+=(ll)siz[fa[u]]*siz[fa[v]]*E[k][i].w;
                Union(u,v);
            }
        }
    }
    // printf("%lld\n",ans[0]);
    // printf("%lld\n",ans[1]);
    printf("%lld\n",ans[1]-ans[0]);
    return 0;
}