#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define root 1,n,1
#define ls (rt<<1)
#define rs (rt<<1|1)
#define lson l,mid,rt<<1
#define rson mid+1,r,rt<<1|1
#define pd __gnu_pbds
inline ll read() {
	ll x=0,w=1;char ch=getchar();
	for(;ch>'9'||ch<'0';ch=getchar()) if(ch=='-') w=-1;
	for(;ch>='0'&&ch<='9';ch=getchar()) x=x*10+ch-'0';
	return x*w;
}
inline void print(__int128 x){
	if(x<0) {putchar('-');x=-x;}
	if(x>9) print(x/10);
	putchar(x%10+'0');
}
#define maxn 1000010
#define int long long
const double eps=1e-8;
#define	int_INF 0x3f3f3f3f
#define ll_INF 0x3f3f3f3f3f3f3f3f
int a[maxn];int x[maxn];int t[maxn];
signed main() {
	int T=read();
	while(T--) {
		int n=read();int m=read();
		int cnt=0;
		for(int i=1;i<=n;i++) {
			a[i]=read();
			cnt+=a[i];
		}
		for(int i=1;i<=m;i++) {
			x[i]=read();t[i]=read();
		}
		m++;
		x[m]=1e18;
		int sum=0;int ans=-1;
		for(int i=1;i<=m;i++) {
			if(x[i]>cnt+sum) {
				ans=cnt+sum;
				break;
			}
			if(sum+a[t[i]]>x[i]) {
				sum=x[i];
			}
			else {
				sum+=a[t[i]];
			}
//			cout<<i<<","<<sum<<endl;
		}
		cout<<ans<<endl;
	}
	return 0;
}