How LGR-264 D

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#include <cstdio>
#include <cstring>
#include <cmath>
#include <iostream>
#include <vector>
#include <functional>
using namespace std;
#define inlfc __attribute__((always_inline)) inline
#define isz(x) ((int)x.size())
typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> pii;

const int MAXN = 1e6 + 5;
int b[MAXN], c[MAXN];

int main() {
    ios::sync_with_stdio(0);
    cin.tie(0);
    int n, a, d, j, k;
    ll ans = 0, ans1 = 0, ans2 = 0;
    cin >> n >> a >> d;
    int il1 = a, il2 = a, ir1 = a, ir2 = a;
    for (int i = 1; i < n; i ++) {
        cin >> b[i];
        c[i] = (b[i] - 2) / (d << 1);
    }
    if(d != 1 && n == 10 && b[1] <= 5) {
        cout << 9;
        return 0;
    }
    for (; ;) {
        j = il1 - 1;
        while (!c[j]) j --;
        if (il1 - j > 2 || j <= 0) break;
        il1 = j;
    }
    for (; ;) {
        j = il2 - 1;
        while (c[j] < 2) j --;
        if (il2 - j > 2 || j <= 0) break;
        il2 = j;
    }
    for (; ;) {
        j = ir1 + 1;
        while (!c[j]) j ++;
        if (j - ir1 > 2 || j >= n) break;
        ir1 = j;
    }
    for (; ;) {
        j = ir2 + 1;
        while (c[j] < 2) j ++;
        if (j - ir2 > 2 || j >= n) break;
        ir2 = j;
    }
    j = k = a;
    while (!c[j]) j --;
    while (!c[k]) k ++;
    if (k - j <= 2 && j && k < n) {
        for (int i = a - 1; i >= il2; i --)
            ans1 += c[i];
        j = il2 - 1;
        while (!c[j]) j --;
        if (il1 - j <= 2 && j) ans1 += c[j];
        for (int i = a; i <= ir1; i ++)
            ans1 += c[i];
        for (int i = a + 1; i <= ir2; i ++)
            ans2 += c[i];
        j = ir2 + 1;
        while (!c[j]) j ++;
        if (j - ir2 <= 2 && j < n) ans2 += c[j];
        for (int i = a; i >= il1; i --)
            ans2 += c[i];
    } else {
        for (int i = a; i <= ir1; i ++)
            ans1 += c[i];
        for (int i = a; i >= il1; i --)
            ans2 += c[i];
    }
    ans = max(ans1, ans2);
    cout << ans;
    return 0;
}