#27484: _CPP
11030067@mail.hpsh.tp.edu.tw
(和平110級鄧雨珊)
int main(){
int n;
while(cin >> n){
int sum=0, bun;
for(int i=1; i<=n; i++){
cin >> bun;
sum+=bun*i;
}
cout<<sum<<endl;
}
}