#include <bits/stdc++.h>
using namespace std;
const int nmx = 501;
#define ll long long
ifstream fin("podm.in");
ofstream fout("podm.out");
#define cin fin
#define cout fout
int main(){
    int n;
    cin >> n;
    n++;
    vector<int> a(n);
    for(int i=0;i<n;i++){
        cin >> a[i];
    }
    int64_t ans = 0;
    for(;;){
        int mx = 0, mxi=-1;
        for(int j=1;j<a.size()-1;j++){
            if(mx < a[j]){
                mx = a[j];
                mxi = j;
            }
        }
        if(mxi==-1)
            break;
        ans += a[mxi]* 1ll * a[mxi-1] * a[mxi+1];
        a.erase(a.begin()+mxi);
    }
    cout << ans;
}