#include<bits/stdc++.h>

 #define LL long long

 using namespace std;

 const int MAXN = 1e5+;

 const int MOD = ;

 LL a[MAXN];

 int n;

 LL quick(LL a,LL x)

 {

     LL r = ;

     while(x>)

     {

         if (x&)

         {

             r = (r*a)%MOD;

             x--;

         }

         a = a%MOD*a%MOD;

         x>>=;

     }

     return r%MOD;

 }

 int main()

 {

     scanf("%d",&n);

     for (int i = ;i<n;i++)

         scanf("%lld",&a[i]);

     LL sum = ;

     for (int i = ;i<n;i++)

         sum = (sum + quick(a[i],i+))%MOD;

     printf("%lld\n",sum);

     return ;

 }