#include<bits/stdc++.h>
using namespace std;
int mp[5005];
long long mod=1e9+7;
int solve(int n)
{
    int i,ans=0;
    for(i=1;i<=n/2;i++)
    {
        if(i==n-i&&mp[i]>=2)
        {
            int m=mp[i];
            ans+=((m*(m-1))%mod)/2;
        }
        else if(mp[i]>=1&&mp[n-i]>=1)
        {
            ans+=(mp[i]*mp[n-i])%mod;
        }
    }
    return ans%mod;
}
int main()
{
    memset(mp,0,sizeof(mp));
    int n,a,i;
    long long ans=0;
    scanf("%d",&n);
    for(i=1;i<=n;i++)
    {
        scanf("%d",&a);
        mp[a]++;
    }
    for(i=1;i<=5000;i++)
    {
        if(mp[i]>=2)
        {
            int m=mp[i];
            ans+=((solve(i)*((m*(m-1))%mod))%mod)/2;
            ans=ans%mod;
        }
    }
    printf("%lld\n",ans);
    return 0;
}