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| #include <bits/stdc++.h>
#define DBG(x) cerr << #x << " = " << x << endl
using namespace std;
typedef long long LL;
#define iall 1, n, 1
#define lrrt int l, int r, int rt
#define lson l, mid, rt << 1
#define rson mid + 1, r, rt << 1 | 1
const int MAXN = 500000 + 16;
const LL INF = 0x7F7F7F7F7F7F7F7F;
LL a[MAXN], sum[MAXN];
LL max_tree[MAXN << 2], min_tree[MAXN << 2];
int STK[MAXN], top;
int L[MAXN], R[MAXN];
int n;
void build(lrrt) {
max_tree[rt] = min_tree[rt] = 0;
if (l == r) {
return;
}
int mid = (l + r) >> 1;
build(lson);
build(rson);
}
void add(lrrt, int x, int v) {
if (l == r) {
max_tree[rt] = min_tree[rt] = v;
return;
}
int mid = (l + r) >> 1;
if (x <= mid) add(lson, x, v);
else add(rson, x, v);
max_tree[rt] = max(max_tree[rt << 1], max_tree[rt << 1 | 1]);
min_tree[rt] = min(min_tree[rt << 1], min_tree[rt << 1 | 1]);
}
LL query_min(lrrt, int x, int y) {
if (x <= l && r <= y) {
return min_tree[rt];
}
int mid = (l + r) >> 1;
if (x > mid) return query_min(rson, x, y);
else if (y <= mid) return query_min(lson, x, y);
else return min(query_min(lson, x, y), query_min(rson, x, y));
}
LL query_max(lrrt, int x, int y) {
if (x <= l && r <= y) {
return max_tree[rt];
}
int mid = (l + r) >> 1;
if (x > mid) return query_max(rson, x, y);
else if (y <= mid) return query_max(lson, x, y);
else return max(query_max(lson, x, y), query_max(rson, x, y));
}
LL get_max(int x, int y) {
if (y == 0)
return 0;
if (x == 0) {
return max(LL(0), query_max(iall, 1, y));
}
return query_max(iall, x, y);
}
void get_lr() {
top = 0;
for (int i = 1; i <= n; ++i) {
L[i] = i;
while (top && a[i] < a[STK[top]]) {
L[i] = L[STK[top]];
R[STK[top]] = i - 1;
--top;
}
STK[++top] = i;
}
while (top) {
R[STK[top--]] = n;
}
}
int main(int argc, char **argv) {
while (~scanf("%d", &n)) {
for (int i = 1; i <= n; ++i) scanf("%lld", &a[i]); a[n + 1] = -INF;
for (int i = 1; i <= n; ++i) sum[i] = sum[i - 1] + a[i];
get_lr();
build(iall);
for (int i = 1; i <= n; ++i) add(iall, i, sum[i]);
LL ans = -INF;
for (int i = 1; i <= n; ++i) {
if (a[i] >= 0) {
LL tmp = a[i] * (sum[R[i]] - sum[L[i] - 1]);
ans = max(ans, tmp);
} else {
LL sr = query_min(iall, i, R[i]);
LL sl = get_max(L[i] - 1, i - 1);
LL tmp = a[i] * (sr - sl);
ans = max(ans, tmp);
}
}
printf("%lld\n", ans);
}
}
|