import java.util.*;

public class Main {
    
    public static void main(String[] args) throws Exception {
        
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        long ans = 0;
        for( int i = 0; i < N; i++ ) {
            long A = sc.nextInt();
            ans += A*(i+1)*(N-i);
        }
        
        System.out.println(ans);
        
    }
    
}