#include "bits/stdc++.h"
#include "atcoder/all"
using namespace std;
using namespace atcoder;
using ll=long long;
using mint=modint998244353;
#define rep3(i,a,b) for(int i=a;i<(b);i++)
#define rep2(i,n) rep3(i,0,n)
#define overload(a,b,c,d,...) d
#define rep(...) overload(__VA_ARGS__,rep3,rep2)(__VA_ARGS__)
#define all(x) x.begin(),x.end()
template<typename T>
istream&operator>>(istream&is,vector<T>&a){
	for(T&x:a)is>>x;
	return is;
}
template<typename T>
ostream&operator<<(ostream&os,const vector<T>&a){
	os<<'{';
	for(const T&x:a)os<<x<<',';
	os<<'}';
	return os;
}
template<typename T>
void operator++(vector<T>&a,int){
	for(T&x:a)x++;
}
template<typename T>bool chmin(T&a,T b){
	if(a>b){
		a=b;
		return true;
	}
	return false;
}
template<typename T>bool chmax(T&a,T b){
	if(a<b){
		a=b;
		return true;
	}
	return false;
}
#ifdef LOCAL
template<typename T>
void debug_rec(T a){
	cerr<<' '<<a<<'\n';
}
template<typename T1,typename... T2>
void debug_rec(T1 a,T2... b){
	cerr<<' '<<a;
	debug_rec(b...);
}
template<typename T1,typename... T2>
void debug(T1 a,T2... b){
	cerr<<"debug";
	debug_rec(a,b...);
}
#else
#define debug(...)
#endif
int main(){
	int n;
	cin>>n;
	vector<ll>a(n);
	cin>>a;
	ll ans=0;
	rep(i,n)ans+=a[i]*(i-(n-i-1));
	cout<<ans<<endl;
}