#include <bits/stdc++.h>
using namespace std;
#define Mod 1000000007
#define int long long int
#define yes cout<<"Yes"<<endl;
#define no cout<<"No"<<endl;
int GCD(int a, int b) {
    if (a == 0)
        return b;
    return GCD(b % a, a);
}
void soln()
{
    int b,n,x,m,y,z,cnt=0,sum=0;
    cin>>n;
    int a[n+5];
    for(int i=0;i<n;i++)cin>>a[i];
 
    for(int i=n;i>=0;i--){
    	sum += (a[i]*i);
    }
    cout<<sum<<endl;
}
signed main()
{
    int tc = 1;
    //cin>>tc;
    while(tc--)
    {
        soln();
    }
}
 
 

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