#include <bits/stdc++.h>
using namespace std;
#define int long long
#define sz(x) (int)x.size()
#define all(x) x.begin() , x.end()
struct CHT{
deque<pair<int,int>>dq;
void add(int e , int f){
while(sz(dq) > 1){
int a = dq[sz(dq)-2].first;
int b = dq[sz(dq)-2].second;
int c = dq[sz(dq)-1].first;
int d = dq[sz(dq)-1].second;
if((f-b) * (a-c) <= (a-e) * (d-b))dq.pop_back();
else break;
}
dq.push_back({e,f});
}
int query(int x){
while(sz(dq) > 1){
int a = dq[0].first;
int b = dq[0].second;
int c = dq[1].first;
int d = dq[1].second;
if(d-b <= (a-c) * x){
dq.pop_front();
}
else break;
}
return dq[0].first * x + dq[0].second;
}
} cht;
void solve(){
int n;
cin >> n;
int arr[n];
for(int i = 0;i<n;i++)cin >> arr[i];
int maxi = arr[0] , premax[n];
memset(premax , 0 , sizeof(premax));
premax[0] = 1;
for(int i = 1;i<n;i++){
if(arr[i] > maxi){
premax[i] = 1;
maxi = arr[i];
}
}
cht.add(n , 0);
int dp[n] , ans = 0;
for(int i = 0;i<n;i++){
if(premax[i] == 0)continue;
int ptr = i+1;
while(ptr < n and premax[ptr] == 0)ptr++;
ptr--;
dp[i] = cht.query(arr[i]);
// cout << i << " : " << dp[i] << " , ptr : " << ptr << endl;
ans = dp[i];
cht.add(n - ptr - 1 , dp[i]);
// cout << "added : " << n-ptr-1 << " " << dp[i] << endl;
}
cout << ans << endl;
}
signed main(){
ios_base::sync_with_stdio(0);cin.tie(0);
int testcase=1;//cin >> testcase;
while(testcase--)solve();
cerr << 1000.0 * clock() / CLOCKS_PER_SEC << " ms" << endl;
}
