#include<bits/stdc++.h>
using namespace std;

typedef long long int           ll;
typedef unsigned long long int  ull;
typedef vector<int>             vi;
typedef vector<ll>              vll;
typedef vector<vi>              vvi;
typedef pair<int,int>           pii;
typedef vector< pii >           vpii;
typedef set<int>                sti;

#define pb                      push_back
#define pob                     pop_back
#define mp                      make_pair
#define ff                      first
#define ss                      second
#define loop1(i,n)              for(int i=1; i<=int(n); i++)
#define loop(i,y)               for(int i=0; i<int(y); i++)
#define rloop(i,y)              for(int i=int(y); i>0; i--)
#define rloop1(i,y)             for(int i=int(y)-1; i>=0; i--)
#define read()                  freopen("input.txt", "r", stdin)
#define write()                 freopen("output.txt", "w", stdout)
#define cspf(i)                 printf("Case %d: ", i)
#define all(v)                  v.begin(),v.end()
#define rall(v)                 v.rbegin(),v.rend()
/// Constants
#define eps                     1e-9
#define PI                      acos(-1.0)  // 3.1415926535897932

ll vt[200009],in[200009],out[200009];
int main()
{
    ll t,n,m,i,x,y,c,sm;
    freopen("bugged.in","r",stdin);
    scanf("%lld",&t);
    while(t--){
        sm=0;
        c=0;
        scanf("%lld %lld",&n,&m);
        loop(i,n){
            scanf("%lld",&vt[i]);
        }
        memset(in,0,sizeof(in));
        memset(out,0,sizeof(out));
        loop(i,m){
            scanf("%lld %lld",&x,&y);
            in[x-1]++;
            out[y-1]++;
            sm+=abs(vt[x-1]-vt[y-1]);
        }
        loop(i,n){
            if(in[i]==out[i])
                continue;
            c++;
        }
        if(c==0)
            printf("%lld\n",sm);
        else
            printf("-1\n");
    }
    return 0;
}