Alice and Bob begin their day with a quick game. They first choose a starting number X0 ≥ 3 and try to reach one million by the process described below. 

Alice goes first and then they take alternating turns. In the i-th turn, the player whose turn it is selects a prime number smaller than the current number, and announces the smallest multiple of this prime number that is not smaller than the current number.

Formally, he or she selects a prime p < Xi - 1 and then finds the minimum Xi ≥ Xi - 1 such that p divides Xi. Note that if the selected prime p already divides Xi - 1, then the number does not change.

Eve has witnessed the state of the game after two turns. Given X2, help her determine what is the smallest possible starting number X0. Note that the players don't necessarily play optimally. You should consider all possible game evolutions.

Input

The input contains a single integer X2 (4 ≤ X2 ≤ 106). It is guaranteed that the integer X2 is composite, that is, is not prime.

Output

Output a single integer — the minimum possible X0.

Examples

Input

14


Output

6


Input

20


Output

15


Input

8192


Output

8191

Note

In the first test, the smallest possible starting number is X0 = 6. One possible course of the game is as follows: 

  * Alice picks prime 5 and announces X1 = 10
  * Bob picks prime 7 and announces X2 = 14. 



In the second case, let X0 = 15. 

  * Alice picks prime 2 and announces X1 = 16
  * Bob picks prime 5 and announces X2 = 20. 

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

public class Q3 {

    public static int div(int arr[],int N){
        for(int i=N/2;i>=0;i--){
            if(arr[i]==0 && N%i==0)
                return i;
        }
        return  N;
    }

    public static void main(String[] args) {
        InputReader in = new InputReader(true);
        PrintWriter out = new PrintWriter(System.out);
        int n =in.nextInt();
        int prime[]=new int[(int)1e6+1];
        for(int i=2;i<prime.length;i++){
            if(prime[i]==0) {
                for (int j = i * 2; j < prime.length; j += i)
                    prime[j] = i;
            }
            prime[i]=i-prime[i]+1;
        }

        int min=n;
        for (int x1=prime[n];x1<=n;x1++) {
            min=Math.min(min,prime[x1]);
        }
        System.out.println(min);



            //        int st[]=new int[4*n];
//        create(0,n-1,arr,1,st);
//
//        for(int i=0;i<st.length;i++)
//            System.out.print(st[i]+" ");
//
//        fetch(st,0,n-1,1,0,n-1);
        out.close();
    }

    static int fetch(int st[],int l,int r,int index,int left,int right){

        if(right<l || left>r || l>r){
            return Integer.MAX_VALUE;
        }
        if(left<=l && r<=right)
            return st[index];
        int mid=(l+r)/2;
        int a =fetch(st,l,mid,index*2,left,right);
        int b=fetch(st,mid+1,r,index*2+1,left,right);
        return Math.min(a,b);
    }

    static int create(int l,int r,int arr[],int index,int st[]) {
        if(l>r)
            return Integer.MAX_VALUE;
        if(l==r){
            st[index]=arr[l];
            return arr[l];
        }
        int mid=(l+r)/2;
        int a =create(l,mid,arr,index*2,st);
        int b =create(mid+1,r,arr,index*2+1,st);
        st[index]=Math.min(a,b);
        return st[index];
    }


    static class InputReader {
        int[][] packU(int n, int[] from, int[] to) {
            int[][] g = new int[n][];
            int[] p = new int[n];
            for (int f : from)
                p[f]++;
            for (int t : to)
                p[t]++;
            for (int i = 0; i < n; i++)
                g[i] = new int[p[i]];
            for (int i = 0; i < from.length; i++) {
                g[from[i]][--p[from[i]]] = to[i];
                g[to[i]][--p[to[i]]] = from[i];
            }
            return g;
        }

        InputStream is;

        public InputReader(boolean onlineJudge) {
            is = System.in;
        }

        byte[] inbuf = new byte[1024];
        public int lenbuf = 0, ptrbuf = 0;

        int readByte() {
            if (lenbuf == -1)
                throw new InputMismatchException();
            if (ptrbuf >= lenbuf) {
                ptrbuf = 0;
                try {
                    lenbuf = is.read(inbuf);
                } catch (IOException e) {
                    throw new InputMismatchException();
                }
                if (lenbuf <= 0)
                    return -1;
            }
            return inbuf[ptrbuf++];
        }

        boolean isSpaceChar(int c) {
            return !(c >= 33 && c <= 126);
        }

        int skip() {
            int b;
            while ((b = readByte()) != -1 && isSpaceChar(b))
                ;
            return b;
        }

        double nextDouble() {
            return Double.parseDouble(next());
        }

        char nextChar() {
            return (char) skip();
        }

        String next() {
            int b = skip();
            StringBuilder sb = new StringBuilder();
            while (!(isSpaceChar(b))) { // when nextLine, (isSpaceChar(b) && b != ' ')
                sb.appendCodePoint(b);
                b = readByte();
            }
            return sb.toString();
        }

        String nextLine() {
            int b = skip();
            StringBuilder sb = new StringBuilder();
            while ((!isSpaceChar(b) || b == ' ')) { // when nextLine, (isSpaceChar(b) && b != ' ')
                sb.appendCodePoint(b);
                b = readByte();
            }
            return sb.toString();
        }

        char[] next(int n) {
            char[] buf = new char[n];
            int b = skip(), p = 0;
            while (p < n && !(isSpaceChar(b))) {
                buf[p++] = (char) b;
                b = readByte();
            }
            return n == p ? buf : Arrays.copyOf(buf, p);
        }

        int nextInt() {
            int num = 0, b;
            boolean minus = false;
            while ((b = readByte()) != -1 && !((b >= '0' && b <= '9') || b == '-'))
                ;
            if (b == '-') {
                minus = true;
                b = readByte();
            }

            while (true) {
                if (b >= '0' && b <= '9') {
                    num = num * 10 + (b - '0');
                } else {
                    return minus ? -num : num;
                }
                b = readByte();
            }
        }

        long nextLong() {
            long num = 0;
            int b;
            boolean minus = false;
            while ((b = readByte()) != -1 && !((b >= '0' && b <= '9') || b == '-'))
                ;
            if (b == '-') {
                minus = true;
                b = readByte();
            }

            while (true) {
                if (b >= '0' && b <= '9') {
                    num = num * 10 + (b - '0');
                } else {
                    return minus ? -num : num;
                }
                b = readByte();
            }
        }

        char[][] nextMatrix(int n, int m) {
            char[][] map = new char[n][];
            for (int i = 0; i < n; i++)
                map[i] = next(m);
            return map;
        }

        int[] nextIntArray(int n) {
            int[] a = new int[n];
            for (int i = 0; i < n; i++)
                a[i] = nextInt();
            return a;
        }

        long[] nextLongArray(int n) {
            long[] a = new long[n];
            for (int i = 0; i < n; i++)
                a[i] = nextLong();
            return a;
        }

        int[][] next2DInt(int n, int m) {
            int[][] arr = new int[n][];
            for (int i = 0; i < n; i++) {
                arr[i] = nextIntArray(m);
            }
            return arr;
        }

        long[][] next2DLong(int n, int m) {
            long[][] arr = new long[n][];
            for (int i = 0; i < n; i++) {
                arr[i] = nextLongArray(m);
            }
            return arr;
        }

        int[] shuffle(int[] arr) {
            Random r = new Random();
            for (int i = 1, j; i < arr.length; i++) {
                j = r.nextInt(i);
                int c = arr[i];
                arr[i] = arr[j];
                arr[j] = c;
            }
            return arr;
        }

        long[] shuffle(long[] arr) {
            Random r = new Random();
            for (int i = 1, j; i < arr.length; i++) {
                j = r.nextInt(i);
                long c = arr[i];
                arr[i] = arr[j];
                arr[j] = c;
            }
            return arr;
        }

        int[] uniq(int[] arr) {
            Arrays.sort(arr);
            int[] rv = new int[arr.length];
            int pos = 0;
            rv[pos++] = arr[0];
            for (int i = 1; i < arr.length; i++) {
                if (arr[i] != arr[i - 1]) {
                    rv[pos++] = arr[i];
                }
            }
            return Arrays.copyOf(rv, pos);
        }

        long[] uniq(long[] arr) {
            Arrays.sort(arr);
            long[] rv = new long[arr.length];
            int pos = 0;
            rv[pos++] = arr[0];
            for (int i = 1; i < arr.length; i++) {
                if (arr[i] != arr[i - 1]) {
                    rv[pos++] = arr[i];
                }
            }
            return Arrays.copyOf(rv, pos);
        }

        int[] reverse(int[] arr) {
            int l = 0, r = arr.length - 1;
            while (l < r) {
                arr[l] = arr[l] ^ arr[r];
                arr[r] = arr[l] ^ arr[r];
                arr[l] = arr[l] ^ arr[r];
                l++;
                r--;
            }
            return arr;
        }

        long[] reverse(long[] arr) {
            int l = 0, r = arr.length - 1;
            while (l < r) {
                arr[l] = arr[l] ^ arr[r];
                arr[r] = arr[l] ^ arr[r];
                arr[l] = arr[l] ^ arr[r];
                l++;
                r--;
            }
            return arr;
        }

        int[] compress(int[] arr) {
            int n = arr.length;
            int[] rv = Arrays.copyOf(arr, n);
            rv = uniq(rv);
            for (int i = 0; i < n; i++) {
                arr[i] = Arrays.binarySearch(rv, arr[i]);
            }
            return arr;
        }

        long[] compress(long[] arr) {
            int n = arr.length;
            long[] rv = Arrays.copyOf(arr, n);
            rv = uniq(rv);
            for (int i = 0; i < n; i++) {
                arr[i] = Arrays.binarySearch(rv, arr[i]);
            }
            return arr;
        }

        void deepFillInt(Object array, int val) {
            if (!array.getClass().isArray()) {
                throw new IllegalArgumentException();
            }
            if (array instanceof int[]) {
                int[] intArray = (int[]) array;
                Arrays.fill(intArray, val);
            } else {
                Object[] objArray = (Object[]) array;
                for (Object obj : objArray) {
                    deepFillInt(obj, val);
                }
            }
        }

        void deepFillLong(Object array, long val) {
            if (!array.getClass().isArray()) {
                throw new IllegalArgumentException();
            }
            if (array instanceof long[]) {
                long[] intArray = (long[]) array;
                Arrays.fill(intArray, val);
            } else {
                Object[] objArray = (Object[]) array;
                for (Object obj : objArray) {
                    deepFillLong(obj, val);
                }
            }
        }

    }

}


