easy_sum

# include <fstream>
#define MOD 1000000007ULL
using namespace std;
ifstream f("easy_sum.in");
ofstream g("easy_sum.out");
int n,x;
unsigned long long int s=0ULL;

int main()
{
    f>>n;
    for(int i=1;i<=n;++i)
        f>>x,s+=(n-i+1ULL)*i*x,s%=MOD;
    g<<s;
    return 0;
}