#include <bits/stdc++.h>
using namespace std;
#define LL long long
struct segtree {
int l, r, mid;
LL val = 0, lazy = 0;
segtree *lc, *rc;
segtree(int L, int R) {
l = L;
r = R;
mid = (l + r) / 2;
if (l != r) {
lc = new segtree(l, mid);
rc = new segtree(mid + 1, r);
}
}
void apply(LL X) {
// val += X;
val += X * (r - l + 1);
lazy += X;
}
void push() {
if (l == r) return;
lc->apply(lazy);
rc->apply(lazy);
lazy = 0;
}
void update(int L, int R, LL X) {
push();
if (l == L && r == R) {
apply(X);
return;
}
else if (R <= mid) lc->update(L, R, X);
else if (L >= mid + 1) rc->update(L, R, X);
else {
lc->update(L, mid, X);
rc->update(mid + 1, R, X);
}
// val = min(lc->val, rc->val);
val = lc->val + rc->val;
}
LL query(int L, int R) {
push();
if (l == L && r == R) return val;
else if (R <= mid) return lc->query(L, R);
else if (L >= mid + 1) return rc->query(L, R);
else {
// return min(lc->query(L, mid), rc->query(mid + 1, R));
return lc->query(L, mid) + rc->query(mid + 1, R);
}
}
//segroot = new segtree(0, n - 1)
} *segroot;
int main() {
ios::sync_with_stdio(false), cin.tie(0);
int n;
cin >> n;
long long ans = 0;
vector<long long> a(n + 1);
vector<bool> b(n + 1, false);
for (int i = 1; i <= n; i++) {
cin >> a[i];
}
int l = 2, r = n - 1;
while (l <= n && a[l] > a[l - 1]) l++;
while (r >= 1 && a[r] > a[r + 1]) r--;
if (l > n || r < 1) {
cout << "0\n";
return 0;
}
segroot = new segtree(0, n + 1);
for (int i = 1; i <= n; i++) {
segroot->update(i, i, a[i]);
}
while (l <= r) {
long long L = segroot->query(l, l);
long long L1 = segroot->query(l-1, l-1);
long long R = segroot->query(r, r);
long long R1 = segroot->query(r+1, r+1);
long long add = min(abs(L - L1), abs(R - R1)) + 1;
ans += add;
segroot->update(l, r, add);
while (l <= n && (segroot->query(l, l)) > (segroot->query(l-1, l-1))) {
l++;
}
while (r >= 1 && (segroot->query(r, r)) > (segroot->query(r+1, r+1))) {
r--;
}
}
if (l <= n && r >= 1 && a[l] == a[r]) ans++;
cout << ans << endl;
return 0;
}
