#include <iostream>
using namespace std;

int main(int argc, char** argv) {
unsigned int n,d[1000],o=0,i;
//cout<<"請輸入天數"<<endl;
cin>>n;
//cout<<"請個別輸入每天買的個數"<<endl;
for(i=1;n>=i;i++){
cin>>d[i];
o+=d[i]*i;
}
cout<<o<<endl;
return 0;
}