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public static void main(String[] args) throws IOException {

        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

        StreamTokenizer in = new StreamTokenizer(br);

        PrintWriter out = new PrintWriter(new OutputStreamWriter(System.out));

        in.nextToken();
        int n = (int) in.nval;

        long[] a = new long[n];

        for (int i = 0; i < n; i++) {
            in.nextToken();
            a[i] = (long) in.nval;
        }

        long maxU = Long.MIN_VALUE;
        long minU = Long.MAX_VALUE;
        long maxV = Long.MIN_VALUE;
        long minV = Long.MAX_VALUE;

        for (long i = 0; i < n; i++) {
            // 计算当前位置的索引（从1开始，而非0）
            long idx = i + 1;
            long val = a[(int) i];

            // 计算u值：位置索引的平方 + 数值的平方
            long u = idx * idx + val * val;
            // 计算v值：位置索引的平方 - 数值的平方
            long v = idx * idx - val * val;

            maxU = Math.max(maxU, u);
            minU = Math.min(minU, u);

            maxV = Math.max(maxV, v);
            minV = Math.min(minV, v);

        }
        long dist = Math.max(maxU - minU, maxV - minV);
        
        out.println(dist);

        out.flush();
        out.close();
        br.close();
    }