Problem:
Score : 300 points

Problem Statement

There are N cities numbered 1 through N, and M bidirectional roads numbered 1 through M.
Road i connects City A_i and City B_i.

Snuke can perform the following operation zero or more times:

Choose two distinct cities that are not directly connected by a road, and build a new road between the two cities.

After he finishes the operations, it must be possible to travel from any city to any other cities by following roads (possibly multiple times).

What is the minimum number of roads he must build to achieve the goal?

Constraints

2 \leq N \leq 100,000

1 \leq M \leq 100,000

1 \leq A_i < B_i \leq N

No two roads connect the same pair of cities.

All values in input are integers.

Input

Input is given from Standard Input in the following format:

N M
A_1 B_1
:
A_M B_M

Output

Print the answer.

Sample Input 1

3 1
1 2

Sample Output 1

1

Initially, there are three cities, and there is a road between City 1 and City 2.

Snuke can achieve the goal by building one new road, for example, between City 1 and City 3.
After that,

We can travel between 1 and 2 directly.

We can travel between 1 and 3 directly.

We can travel between 2 and 3 by following both roads (2 - 1 - 3).

Solution in Java (OpenJDK 11.0.6) (judge verdict: Accepted)

import java.io.*;
import java.util.*;

public class Main {

    public static boolean useInFile = false;
    public static boolean useOutFile = false;

    public static void main(String args[]) throws IOException {
        InOut inout = new InOut();
        Resolver resolver = new Resolver(inout);
        resolver.solve();
        inout.flush();
    }

    private static class Resolver {

        final long LONG_INF = (long) 1e18;
        final int INF = (int) (1e9 + 7);
        final int MOD = 998244353;
        long f[], inv[];
        InOut inout;

        Resolver(InOut inout) {
            this.inout = inout;
        }

        void initF(int n, int mod) {
            f = new long[n + 1];
            f[1] = 1;
            for (int i = 2; i <= n; i++) {
                f[i] = (f[i - 1] * i) % mod;
            }
        }

        void initInv(int n, int mod) {
            inv = new long[n + 1];
            inv[n] = pow(f[n], mod - 2, mod);
            for (int i = inv.length - 2; i >= 0; i--) {
                inv[i] = inv[i + 1] * (i + 1) % mod;
            }
        }

        long cmn(int n, int m, int mod) {
            return f[n] * inv[m] % mod * inv[n - m] % mod;
        }

        int d[] = {0, -1, 0, 1, 0};

        boolean legal(int r, int c, int n, int m) {
            return r >= 0 && r < n && c >= 0 && c < m;
        }

        void dfs(int f, int p, boolean vis[]) {
            List<Integer> es = adj[f];
            vis[f] = true;
            for (int i = 0; i < es.size(); i++) {
                int t = es.get(i);
                if (vis[t]) {
                    continue;
                }
                dfs(t, f, vis);
            }
        }

        void solve() throws IOException {
            int tt = 1;
            boolean hvt = false;
            if (hvt) {
                tt = nextInt();
//                tt = Integer.parseInt(nextLine());
            }
//            initF(2001, INF);
//            initInv(2001, INF);

            for (int cs = 1; cs <= tt; cs++) {
                long rs = 0;
                int n = nextInt();
                int m = nextInt();
                initGraph(n, m, false, false, 1);
                boolean vis[] = new boolean[n + 1];
                for (int i = 1; i <= n; i++) {
                    if (vis[i]) {
                        continue;
                    }
                    rs++;
                    dfs(i, -1, vis);
                }
                rs--;




                format("%d", rs);
//                format("Case #%d: %d", cs, rs);

                if (cs < tt) {
                    format("\n");
//                    format(" ");
                }
//                flush();
            }

            int testtest = 0;
        }

        private void updateSegTree(int n, long l, SegmentTree lft) {
            long lazy;
            lazy = 1;
            for (int j = 1; j <= l; j++) {
                lazy = (lazy + cmn((int) l, j, INF)) % INF;
                lft.modify(1, j, j, lazy);
            }
            lft.modify(1, (int) (l + 1), n, lazy);
        }

        String next() throws IOException {
            return inout.next();
        }

        String next(int n) throws IOException {
            return inout.next(n);
        }

        String nextLine() throws IOException {
            return inout.nextLine();
        }

        int nextInt() throws IOException {
            return inout.nextInt();
        }

        long nextLong(int n) throws IOException {
            return inout.nextLong(n);
        }

        int[] anInt(int i, int j) throws IOException {
            int a[] = new int[j + 1];
            for (int k = i; k <= j; k++) {
                a[k] = nextInt();
            }
            return a;
        }

        long[] anLong(int i, int j, int len) throws IOException {
            long a[] = new long[j + 1];
            for (int k = i; k <= j; k++) {
                a[k] = nextLong(len);
            }
            return a;
        }

        void print(String s, boolean nextLine) {
            inout.print(s, nextLine);
        }

        void format(String format, Object... obj) {
            inout.format(format, obj);
        }

        void flush() {
            inout.flush();
        }

        void swap(long a[], int i, int j) {
            a[i] ^= a[j];
            a[j] ^= a[i];
            a[i] ^= a[j];
        }

        int getP(int x, int p[]) {
            if (p[x] == 0 || p[x] == x) {
                return x;
            }
            return p[x] = getP(p[x], p);
        }

        void union(int x, int y, int p[]) {
            if (x < y) {
                p[y] = x;
            } else {
                p[x] = y;
            }
        }

        boolean topSort() {
            int n = adj2.length - 1;
            int d[] = new int[n + 1];
            for (int i = 1; i <= n; i++) {
                for (int j = 0; j < adj2[i].size(); j++) {
                    d[adj2[i].get(j)[0]]++;
                }
            }
            List<Integer> list = new ArrayList<>();
            for (int i = 1; i <= n; i++) {
                if (d[i] == 0) {
                    list.add(i);
                }
            }
            for (int i = 0; i < list.size(); i++) {
                for (int j = 0; j < adj2[list.get(i)].size(); j++) {
                    int t = adj2[list.get(i)].get(j)[0];
                    d[t]--;
                    if (d[t] == 0) {
                        list.add(t);
                    }
                }
            }
            return list.size() == n;
        }

        class SegmentTreeNode {
            long defaultVal = 0;
            int l, r;
            long val = defaultVal, lazy = defaultVal;

            SegmentTreeNode(int l, int r) {
                this.l = l;
                this.r = r;
            }
        }

        class SegmentTree {
            SegmentTreeNode tree[];
            long inf = Long.MIN_VALUE;

            SegmentTree(int n) {
                assert n > 0;
                tree = new SegmentTreeNode[n << 2];
            }

            SegmentTree build(int k, int l, int r) {
                if (l > r) {
                    return this;
                }
                if (null == tree[k]) {
                    tree[k] = new SegmentTreeNode(l, r);
                }
                if (l == r) {
                    return this;
                }
                int mid = (l + r) >> 1;
                build(k << 1, l, mid);
                build(k << 1 | 1, mid + 1, r);
                return this;
            }

            void pushDown(int k) {
                if (tree[k].l == tree[k].r) {
                    return;
                }
                long lazy = tree[k].lazy;
                tree[k << 1].val += lazy;
                tree[k << 1].lazy += lazy;
                tree[k << 1 | 1].val += lazy;
                tree[k << 1 | 1].lazy += lazy;
                tree[k].lazy = 0;
            }

            void modify(int k, int l, int r, long val) {
                if (tree[k].l >= l && tree[k].r <= r) {
                    tree[k].val += val;
                    tree[k].lazy += val;
                    return;
                }
                int mid = (tree[k].l + tree[k].r) >> 1;
                if (mid >= l) {
                    modify(k << 1, l, r, val);
                }
                if (mid + 1 <= r) {
                    modify(k << 1 | 1, l, r, val);
                }
                tree[k].val = Math.max(tree[k << 1].val, tree[k << 1 | 1].val);
            }

            long query(int k, int l, int r) {
                if (tree[k].l > r || tree[k].r < l) {
                    return inf;
                }
                if (tree[k].lazy != 0) {
                    pushDown(k);
                }
                if (tree[k].l >= l && tree[k].r <= r) {
                    return tree[k].val;
                }
                long ans = Math.max(query(k << 1, l, r), query(k << 1 | 1, l, r));
                if (tree[k].l < tree[k].r) {
                    tree[k].val = Math.max(tree[k << 1].val, tree[k << 1 | 1].val);
                }
                return ans;
            }
        }


        class BinaryIndexedTree {

            int n = 1;
            long C[];

            BinaryIndexedTree(int sz) {
                while (n <= sz) {
                    n <<= 1;
                }
                C = new long[n];
            }

            int lowbit(int x) {
                return x & -x;
            }

            void add(int x, long val) {
                while (x < n) {
                    C[x] += val;
                    x += lowbit(x);
                }
            }

            long getSum(int x) {
                long res = 0;
                while (x > 0) {
                    res += C[x];
                    x -= lowbit(x);
                }
                return res;
            }

            int binSearch(long sum) {
                if (sum == 0) {
                    return 0;
                }
                int n = C.length;
                int mx = 1;
                while (mx < n) {
                    mx <<= 1;
                }
                int res = 0;
                for (int i = mx / 2; i >= 1; i >>= 1) {
                    if (C[res + i] < sum) {
                        sum -= C[res + i];
                        res += i;
                    }
                }
                return res + 1;
            }
        }

        int mnS;
        int mxS;
        Map<Integer, TrieNode> SS = new HashMap<>();

        class TrieNode {
            int cnt = 0;
            boolean isMin = false;
            boolean isMax = false;
            int mnIdx = 26;
            int mxIdx = -1;

            TrieNode next[];

            TrieNode() {
                next = new TrieNode[26];
            }

            private void insert(TrieNode trie, char ch[], int i, int j) {
                while (i < ch.length) {
                    int idx = ch[i] - 'a';
                    if (null == trie.next[idx]) {
                        trie.next[idx] = new TrieNode();
                    }
                    trie.cnt++;
                    int lastMnIdx = trie.mnIdx;
                    int lastMxIdx = trie.mxIdx;
                    trie.mnIdx = Math.min(trie.mnIdx, idx);
                    trie.mxIdx = Math.max(trie.mxIdx, idx);
                    if (trie.isMin && lastMnIdx != trie.mnIdx) {
                        if (lastMnIdx != 26) {
                            notMin(trie.next[lastMnIdx]);
                        }
                        trie.next[trie.mnIdx].isMin = true;
                    }
                    if (trie.isMax && lastMxIdx != trie.mxIdx) {
                        if (lastMxIdx >= 0) {
                            notMax(trie.next[lastMxIdx]);
                        }
                        trie.next[trie.mxIdx].isMax = true;
                    }
                    trie = trie.next[idx];
                    i++;
                }
                SS.put(j + 1, trie);
                if (trie.cnt == 0) {
                    if (trie.isMin) {
                        mnS = j + 1;
                    }
                    if (trie.isMax) {
                        mxS = j + 1;
                    }
                }
            }

            private void notMin(TrieNode trie) {
                while (null != trie) {
                    trie.isMin = false;
                    int val = trie.mnIdx;
                    if (val >= 26 || val < 0 || null == trie.next[val]) {
                        break;
                    }
                    trie = trie.next[val];
                }
            }

            private void notMax(TrieNode trie) {
                while (null != trie) {
                    trie.isMax = false;
                    int val = trie.mxIdx;
                    if (val >= 26 || val < 0 || null == trie.next[val]) {
                        break;
                    }
                    trie = trie.next[val];
                }
            }
        }

        //Binary tree
        class TreeNode {
            int val;
            int tier = -1;
            TreeNode parent;
            TreeNode left;
            TreeNode right;

            TreeNode(int val) {
                this.val = val;
            }
        }

        //binary tree dfs
        void tierTree(TreeNode root) {
            if (null == root) {
                return;
            }
            if (null != root.parent) {
                root.tier = root.parent.tier + 1;
            } else {
                root.tier = 0;
            }
            tierTree(root.left);
            tierTree(root.right);
        }

        //LCA start
        TreeNode[][] lca;
        TreeNode[] tree;

        void lcaDfsTree(TreeNode root) {
            if (null == root) {
                return;
            }
            tree[root.val] = root;
            TreeNode nxt = root.parent;
            int idx = 0;
            while (null != nxt) {
                lca[root.val][idx] = nxt;
                nxt = lca[nxt.val][idx];
                idx++;
            }
            lcaDfsTree(root.left);
            lcaDfsTree(root.right);
        }

        TreeNode lcaTree(TreeNode root, int n, TreeNode x, TreeNode y) throws IOException {
            if (null == root) {
                return null;
            }
            if (-1 == root.tier) {
                tree = new TreeNode[n + 1];
                tierTree(root);
            }
            if (null == lca) {
                lca = new TreeNode[n + 1][31];
                lcaDfsTree(root);
            }
            int z = Math.abs(x.tier - y.tier);
            int xx = x.tier > y.tier ? x.val : y.val;
            while (z > 0) {
                final int zz = z;
                int l = (int) BinSearch.bs(0, 31
                        , k -> zz < (1 << k));
                xx = lca[xx][l].val;
                z -= 1 << l;
            }
            int yy = y.val;
            if (x.tier <= y.tier) {
                yy = x.val;
            }
            while (xx != yy) {
                final int xxx = xx;
                final int yyy = yy;
                int l = (int) BinSearch.bs(0, 31
                        , k -> (1 << k) <= tree[xxx].tier && lca[xxx][(int) k] != lca[yyy][(int) k]);
                xx = lca[xx][l].val;
                yy = lca[yy][l].val;
            }
            return tree[xx];
        }
        //LCA end

        //graph
        List<Integer> adj[];
        List<int[]> adj2[];

        void initGraph(int n, int m, boolean hasW, boolean directed, int type) throws IOException {
            if (type == 1) {
                adj = new List[n + 1];
            } else {
                adj2 = new List[n + 1];
            }
            for (int i = 1; i <= n; i++) {
                if (type == 1) {
                    adj[i] = new ArrayList<>();
                } else {
                    adj2[i] = new ArrayList<>();
                }
            }
            for (int i = 0; i < m; i++) {
                int f = nextInt();
                int t = nextInt();
                if (type == 1) {
                    adj[f].add(t);
                    if (!directed) {
                        adj[t].add(f);
                    }
                } else {
                    int w = hasW ? nextInt() : 0;
                    adj2[f].add(new int[]{t, w});
                    if (!directed) {
                        adj2[t].add(new int[]{f, w});
                    }
                }
            }
        }

        void getDiv(Map<Integer, Integer> map, long n) {
            int sqrt = (int) Math.sqrt(n);
            for (int i = 2; i <= sqrt; i++) {
                int cnt = 0;
                while (n % i == 0) {
                    cnt++;
                    n /= i;
                }
                if (cnt > 0) {
                    map.put(i, cnt);
                }
            }
            if (n > 1) {
                map.put((int) n, 1);
            }
        }

        boolean[] generatePrime(int n) {
            boolean p[] = new boolean[n + 1];
            p[2] = true;

            for (int i = 3; i <= n; i += 2) {
                p[i] = true;
            }

            for (int i = 3; i <= Math.sqrt(n); i += 2) {
                if (!p[i]) {
                    continue;
                }
                for (int j = i * i; j <= n; j += i << 1) {
                    p[j] = false;
                }
            }
            return p;
        }

        boolean isPrime(long n) { //determines if n is a prime number
            int p[] = {2, 3, 5, 233, 331};
            int pn = p.length;
            long s = 0, t = n - 1;//n - 1 = 2^s * t
            while ((t & 1) == 0) {
                t >>= 1;
                ++s;
            }
            for (int i = 0; i < pn; ++i) {
                if (n == p[i]) {
                    return true;
                }
                long pt = pow(p[i], t, n);
                for (int j = 0; j < s; ++j) {
                    long cur = llMod(pt, pt, n);
                    if (cur == 1 && pt != 1 && pt != n - 1) {
                        return false;
                    }
                    pt = cur;
                }
                if (pt != 1) {
                    return false;
                }
            }
            return true;
        }

        long[] llAdd2(long a[], long b[], long mod) {
            long c[] = new long[2];
            c[1] = (a[1] + b[1]) % (mod * mod);
            c[0] = (a[1] + b[1]) / (mod * mod) + a[0] + b[0];
            return c;
        }

        long[] llMod2(long a, long b, long mod) {
            long x1 = a / mod;
            long y1 = a % mod;
            long x2 = b / mod;
            long y2 = b % mod;
            long c = (x1 * y2 + x2 * y1) / mod;
            c += x1 * x2;
            long d = (x1 * y2 + x2 * y1) % mod * mod + y1 * y2;
            return new long[]{c, d};
        }

        long llMod(long a, long b, long mod) {
            if (a > mod || b > mod) {
                return (a * b - (long) ((double) a / mod * b + 0.5) * mod + mod) % mod;
            }
            return a * b % mod;
//        long r = 0;
//        a %= mod;
//        b %= mod;
//        while (b > 0) {
//            if ((b & 1) == 1) {
//                r = (r + a) % mod;
//            }
//            b >>= 1;
//            a = (a << 1) % mod;
//        }
//        return r;
        }

        long pow(long a, long n) {
            long ans = 1;
            while (n > 0) {
                if ((n & 1) == 1) {
                    ans = ans * a;
                }
                a = a * a;
                n >>= 1;
            }
            return ans;
        }

        long pow(long a, long n, long mod) {
            long ans = 1;
            while (n > 0) {
                if ((n & 1) == 1) {
                    ans = llMod(ans, a, mod);
                }
                a = llMod(a, a, mod);
                n >>= 1;
            }
            return ans;
        }

        private long[][] initC(int n) {
            long c[][] = new long[n][n];

            for (int i = 0; i < n; i++) {
                c[i][0] = 1;
            }

            for (int i = 1; i < n; i++) {
                for (int j = 1; j <= i; j++) {
                    c[i][j] = c[i - 1][j - 1] + c[i - 1][j];
                }
            }
            return c;
        }

        /**
         * ps: n >= m, choose m from n;
         */
//        private int cmn(long n, long m) {
//            if (m > n) {
//                n ^= m;
//                m ^= n;
//                n ^= m;
//            }
//            m = Math.min(m, n - m);
//
//            long top = 1;
//            long bot = 1;
//            for (long i = n - m + 1; i <= n; i++) {
//                top = (top * i) % MOD;
//            }
//            for (int i = 1; i <= m; i++) {
//                bot = (bot * i) % MOD;
//            }
//
//            return (int) ((top * pow(bot, MOD - 2, MOD)) % MOD);
//        }

        long[] exGcd(long a, long b) {
            if (b == 0) {
                return new long[] {a, 1, 0};
            }
            long[] ans = exGcd(b, a % b);
            long x = ans[2];
            long y = ans[1] - a / b * ans[2];
            ans[1] = x;
            ans[2] = y;
            return ans;
        }

        long gcd(long a, long b) {
            if (a < b) {
                return gcd(b, a);
            }
            while (b != 0) {
                long tmp = a % b;
                a = b;
                b = tmp;
            }
            return a;
        }

        int[] unique(int a[], Map<Integer, Integer> idx) {
            int tmp[] = a.clone();
            Arrays.sort(tmp);
            int j = 0;
            for (int i = 0; i < tmp.length; i++) {
                if (i == 0 || tmp[i] > tmp[i - 1]) {
                    idx.put(tmp[i], j++);
                }
            }
            int rs[] = new int[j];
            j = 0;
            for (int key : idx.keySet()) {
                rs[j++] = key;
            }
            Arrays.sort(rs);
            return rs;
        }

        boolean isEven(long n) {
            return (n & 1) == 0;
        }

        static class BinSearch {

            static long bs(long l, long r, IBinSearch sort) throws IOException {
                while (l < r) {
                    long m = l + (r - l) / 2;
                    if (sort.binSearchCmp(m)) {
                        l = m + 1;
                    } else {
                        r = m;
                    }
                }
                return l;
            }

            interface IBinSearch {
                boolean binSearchCmp(long k) throws IOException;
            }

        }
    }

    private static class InOut {
        private BufferedReader br;
        private StreamTokenizer st;
        private PrintWriter pw;

        InOut() throws FileNotFoundException {
            if (useInFile) {
                System.setIn(new FileInputStream("resources/inout/in.text"));
            }
            if (useOutFile) {
                System.setOut(new PrintStream("resources/inout/out.text"));
            }
            br = new BufferedReader(new InputStreamReader(System.in));
            st = new StreamTokenizer(br);
            pw = new PrintWriter(new OutputStreamWriter(System.out));
            st.ordinaryChar('\'');
            st.ordinaryChar('\"');
            st.ordinaryChar('/');
        }

        private long[] anLong(int n) throws IOException {
            long a[] = new long[n];
            for (int i = 0; i < n; i++) {
                a[i] = nextInt();
            }
            return a;
        }

        private String next() throws IOException {
            st.nextToken();
            return st.sval;
        }

        private String next(int len) throws IOException {
            char ch[] = new char[len];
            int cur = 0;
            char c;
            while ((c = (char) br.read()) == '\n' || c == '\r' || c == ' ' || c == '\t') ;
            do {
                ch[cur++] = c;
            } while (!((c = (char) br.read()) == '\n' || c == '\r' || c == ' ' || c == '\t'));
            return String.valueOf(ch, 0, cur);
        }

        private int nextInt() throws IOException {
            st.nextToken();
            return (int) st.nval;
        }

        private long nextLong(int n) throws IOException {
            return Long.parseLong(next(n));
        }

        private double nextDouble() throws IOException {
            st.nextToken();
            return st.nval;
        }

        private String[] nextSS(String reg) throws IOException {
            return br.readLine().split(reg);
        }

        private String nextLine() throws IOException {
            return br.readLine();
        }

        private void print(String s, boolean newLine) {
            if (null != s) {
                pw.print(s);
            }
            if (newLine) {
                pw.println();
            }
        }

        private void format(String format, Object... obj) {
            pw.format(format, obj);
        }

        private void flush() {
            pw.flush();
        }
    }

    private static class FFT {
        double[] roots;
        int maxN;

        public FFT(int maxN) {
            this.maxN = maxN;
            initRoots();
        }

        public long[] multiply(int[] a, int[] b) {
            int minSize = a.length + b.length - 1;
            int bits = 1;
            while (1 << bits < minSize) bits++;
            int N = 1 << bits;
            double[] aa = toComplex(a, N);
            double[] bb = toComplex(b, N);
            fftIterative(aa, false);
            fftIterative(bb, false);
            double[] c = new double[aa.length];
            for (int i = 0; i < N; i++) {
                c[2 * i] = aa[2 * i] * bb[2 * i] - aa[2 * i + 1] * bb[2 * i + 1];
                c[2 * i + 1] = aa[2 * i] * bb[2 * i + 1] + aa[2 * i + 1] * bb[2 * i];
            }
            fftIterative(c, true);
            long[] ret = new long[minSize];
            for (int i = 0; i < ret.length; i++) {
                ret[i] = Math.round(c[2 * i]);
            }
            return ret;
        }

        static double[] toComplex(int[] arr, int size) {
            double[] ret = new double[size * 2];
            for (int i = 0; i < arr.length; i++) {
                ret[2 * i] = arr[i];
            }
            return ret;
        }

        void initRoots() {
            roots = new double[2 * (maxN + 1)];
            double ang = 2 * Math.PI / maxN;
            for (int i = 0; i <= maxN; i++) {
                roots[2 * i] = Math.cos(i * ang);
                roots[2 * i + 1] = Math.sin(i * ang);
            }
        }

        int bits(int N) {
            int ret = 0;
            while (1 << ret < N) ret++;
            if (1 << ret != N) throw new RuntimeException();
            return ret;
        }

        void fftIterative(double[] array, boolean inv) {
            int bits = bits(array.length / 2);
            int N = 1 << bits;
            for (int from = 0; from < N; from++) {
                int to = Integer.reverse(from) >>> (32 - bits);
                if (from < to) {
                    double tmpR = array[2 * from];
                    double tmpI = array[2 * from + 1];
                    array[2 * from] = array[2 * to];
                    array[2 * from + 1] = array[2 * to + 1];
                    array[2 * to] = tmpR;
                    array[2 * to + 1] = tmpI;
                }
            }
            for (int n = 2; n <= N; n *= 2) {
                int delta = 2 * maxN / n;
                for (int from = 0; from < N; from += n) {
                    int rootIdx = inv ? 2 * maxN : 0;
                    double tmpR, tmpI;
                    for (int arrIdx = 2 * from; arrIdx < 2 * from + n; arrIdx += 2) {
                        tmpR = array[arrIdx + n] * roots[rootIdx] - array[arrIdx + n + 1] * roots[rootIdx + 1];
                        tmpI = array[arrIdx + n] * roots[rootIdx + 1] + array[arrIdx + n + 1] * roots[rootIdx];
                        array[arrIdx + n] = array[arrIdx] - tmpR;
                        array[arrIdx + n + 1] = array[arrIdx + 1] - tmpI;
                        array[arrIdx] += tmpR;
                        array[arrIdx + 1] += tmpI;
                        rootIdx += (inv ? -delta : delta);
                    }
                }
            }
            if (inv) {
                for (int i = 0; i < array.length; i++) {
                    array[i] /= N;
                }
            }
        }
    }
}