Ari the monster always wakes up very early with the first ray of the sun and the first thing she does is feeding her squirrel.

Ari draws a regular convex polygon on the floor and numbers it's vertices 1, 2, ..., n in clockwise order. Then starting from the vertex 1 she draws a ray in the direction of each other vertex. The ray stops when it reaches a vertex or intersects with another ray drawn before. Ari repeats this process for vertex 2, 3, ..., n (in this particular order). And then she puts a walnut in each region inside the polygon.

<image>

Ada the squirrel wants to collect all the walnuts, but she is not allowed to step on the lines drawn by Ari. That means Ada have to perform a small jump if she wants to go from one region to another. Ada can jump from one region P to another region Q if and only if P and Q share a side or a corner.

Assuming that Ada starts from outside of the picture, what is the minimum number of jumps she has to perform in order to collect all the walnuts?

Input

The first and only line of the input contains a single integer n (3 ≤ n ≤ 54321) - the number of vertices of the regular polygon drawn by Ari.

Output

Print the minimum number of jumps Ada should make to collect all the walnuts. Note, that she doesn't need to leave the polygon after.

Examples

Input

5


Output

9


Input

3


Output

1

Note

One of the possible solutions for the first sample is shown on the picture above.
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.math.BigInteger;
import java.util.ArrayDeque;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.Comparator;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.PriorityQueue;
import java.util.Scanner;
import java.util.Stack;
import java.util.StringTokenizer;


public class CodeForces {

    
    private static boolean sameset(int a, int b, int[] uf) {
        
        return find(a,uf) == find(b,uf);
    }

    private static void union(int a, int b, int[] uf) {
        uf[find(a,uf)] = find(b,uf);
    }

    private static int find(int a, int[] uf) {
        if(a == uf[a])  return a;
        int root = find(uf[a],uf);
        uf[a] = root;
        return root;
    }

    private static void BFS(int i, int[][] G, int[][] path) {
       // System.out.println("source vertex "+i);
        int[] v = new int[G.length]; // current maximum dist in u---v path
        ArrayDeque<Integer> A = new ArrayDeque();
        A.add(i);
        while(A.isEmpty() == false){
            int u = A.pop();
            //System.out.println("for node "+u);
            for(int a=0;a<v.length;a++){
                if(G[u][a] > 0 && v[a]==0 && a!=i){//edge in MST, later make faster
                    //System.out.println(a+" is and edge from "+u);
                    if(G[u][a] > v[u]){
                        //System.out.println(" and it incrases the sub path max ");
                        v[a] = G[u][a];
                    }
                    else    v[a] = v[u];
                    path[i][a] = v[a];
                    path[a][i] = v[a];
                   // System.out.println("finally path from "+i+" to "+a+" is "+path[i][a]);
                    
                    A.add(a);
                }
            }
        }
    }

    private static int numd(int x) {
        Double xx = Double.parseDouble(String.valueOf(x));
        int y = (int) Math.log10(xx);
        return (y+1);
       
         
        
    }

    private static String primeFactor(int n, boolean[] x) {
        String ans = "";
        for(int i=2;i<x.length;i++){
            if(i*i > n) break;
            if(x[i]){
                //System.out.println("testing prome "+i);
                while(n!=1 && i*i <= n){
                    while(n%i==0){
                       // System.out.println(i+" can divide "+n);
                        if(ans.equals(""))  ans=String.valueOf(i);
                        else    ans+=" x "+i;
                        n/=i;
                    }
                    break;
                }
            }
        }
        if(n!=1){
           // System.out.println("Remainig "+n);
            if(ans.equals(""))  ans=String.valueOf(n);
            else    ans+=" x "+n;
        }
        return ans;
    }

    private static String solve(String s) {
        
        
        
        return null;
    }

    //counts the number of divisors using the fundamental theorem of arithmetic
    private static int getDivisorCount(int n) {
        
        int count = 1;
        
        int tmp = n;
        
        for(int i=2;i*i<=n;i=(i==2?3:i+2)){
            
            //System.out.println(i+" is odd");
            
            int pow = 0;
            
            while(n%i==0){
                pow+=1;
                n/=i;
            }
            
            if(pow != 0){
                ///System.out.println(i+" must be a prime");
                count*=(pow+1);
            }
        }
        
        if(n!=1){
            //System.out.println(n+" is the last prime factor");
            count*=2;
        }
        
        //System.out.println("number of divisors of "+tmp+" is "+count);
        return count;
    }

    private static long nchoosek(int n, int k) {
        
        long prod = 1;
        int j = 1;
        
        int st = Math.max(n-k, k)+1;
        int ed = Math.min(n-k, k);
        
        for(int i=st;i<=n;i++){
            for(;j<=ed;j++){
                if(prod%j==0)   prod/=j;
                else break;
            }
            prod*=i;
        }
        
        for(;j<=ed;j++){
            prod/=j;
        }
        
        return prod;
    }
    
    //related to extgcd problems
    private static boolean check() {
        //System.out.println(a+" "+b+" "+c1+" "+c2);
        if(n%ibgcd(a,b)!=0) {
           // System.out.println("not possible");
            return false;
        }
        
        extgcd(a,b);
        long gcd=0,m1=x,m2=y;
        gcd=d;
        m1*=(n/d);
        m2*=(n/d);
        a/=d;
        b/=d;
        
        double f1 = (m1/b);f1*=-1;
        double f2 = (m2/a);
        long le = (long) Math.ceil(f1);
        long re = (long) Math.floor(f2);
        if(le > re) return false;
        long cf=c1*b-c2*a;
        if(cf*le < cf*re){
        
            x = m1+b*le;
            y = m2-a*le;
        }else{
            x = m1+b*re;
            y = m2-a*re;
        }
        //System.out.println("upper and lower are "+le+" "+re);
        
        
        return true;
    }

    private static void extgcd(long a, long b) {
        
        if(b==0){
            x=1;y=0;d=a;return;
        }
        extgcd(b,a%b);
        long x1 = y;
        long y1 = x-(a/b)*y;
        x=x1;
        y=y1;
    }

    private static void floyd_cycle(int z, int I, int m, int x0) {
        
        int tor = func(z,I,m,x0);
        int har = func(z,I,m,tor); //one step ahead of tor
        //System.out.println("initial value for tor and har "+tor+" "+har);
        
        while(tor!=har){
            tor = func(z,I,m,tor);
            har = func(z,I,m,har);
            har = func(z,I,m,har);
            //System.out.println("tor and har "+tor+" "+har);
        }
        
        //at r-x%m now
        int x = 0;
        har = tor;
        tor = x0;
        
        while(har!=tor){
            
            tor = func(z,I,m,tor);
            har = func(z,I,m,har);
            x+=1;
            //System.out.println("findind x tor and har "+tor+" "+har);
        }
        
        //now at first reapting node
        int lam = 1;
        har = func(z,I,m,tor);
        
        while(har!=tor){
            har = func(z,I,m,har);
            lam+=1;
            //System.out.println("finding lam, tor and har "+tor+" "+har);
        }
        
       // return new Pair(z,lam);
    }

   private static int func(int z, int I, int m, int x0) {
        return ((z*x0)%m+I%m)%m;
    }

    private static void dfs(int a, int[][] d, int[] v,int[] p) {
        
        v[a] = 1;
        for(int i=0;i<v.length;i++){
            if(i!=a && d[i][a]!=0){
                if(v[i]==0){
                   // System.out.println("dfsing "+i);
                    p[i]=a;
                    dfs(i,d,v,p);
                }else if(p[a] != i && a<i){
                   // System.out.println(a+" and "+i+" causing cycle"+p[i]);
                    cycle=true;
                }
            }
        }
        
    }

    private static void dolve(int x, int[] a) {
        //find sors of x
        int cnt = 0;
        for(int i=2;i<=Math.sqrt(x);i=(i==2?3:i+2)){
            int pow = 0;
            while(x%i==0){
                x/=i;
                pow+=1;
            }
            if(pow!=0){
                for(int j=1;j<=pow;j++){
                    long f = (long) Math.pow(i, j);
                    
                    if(f<a.length){
                        a[Integer.parseInt(String.valueOf(f))]=1;
                        //System.out.println("ading "+Integer.parseInt(String.valueOf(f)));
                    }
                    
                }
            }
        }
        
        if(x!=1){
            //System.out.println("ading "+x);
            if(x<a.length)  a[x]=1;
        }
    }

    

    private static long search(long max, long tmp, long a, long b) {
        
        long lo = 0;
        long hi = max;
        
        while(lo < hi){
            
            long mid = (lo+hi)>>1;
            
            long k = mid*a;
            k/=b;
            if(k==tmp)  hi=mid;
            else    lo = mid+1;
        }
        
        return lo;
    }

    

    private static int palindrome(int i, int j, String s, int[][] dp) {
        //if(i > j)   System.out.println("PLEASE STOP");
        int ret = 0;
        if(i==j)    {
            dp[i][j]=ret;
            return ret;
        }
        if(i+1==j && s.charAt(i)==s.charAt(j))  {
            dp[i][j]=ret;
            return ret;
        }
        if(i+1==j && s.charAt(i)!=s.charAt(j))  {
            
            ret = 1;
            dp[i][j]=ret;
            return ret;
        }
        
        if(s.charAt(i) == s.charAt(j)){
            
            ret = dp[i+1][j-1]==-1 ? palindrome(i+1,j-1,s,dp) : dp[i+1][j-1];
            //ret = 2+ sub;
            dp[i][j]=ret;
            return ret;
        }
        else{
            int sub1 = dp[i+1][j]==-1 ? palindrome(i+1,j,s,dp) : dp[i+1][j];
            int sub2 = dp[i][j-1]==-1 ? palindrome(i, j-1,s,dp) : dp[i][j-1];
            int sub3 = dp[i+1][j-1]==-1 ? palindrome(i+1,j-1,s,dp) : dp[i+1][j-1];
            
            ret = Math.min(sub1, sub2);
            ret = Math.min(ret, sub3);
            ret+=1;
            dp[i][j]=ret;
            return ret;
        }
        //return 0;
    }

    private static ArrayList<Integer> dfs_p(int a, int[] v, int[][] g, ArrayList<Integer> A) {
        
        v[a]=1;
        A.add(a);
        
        for(int i=0;i<v.length;i++){
            if(i!=a){
                if(g[a][i]==1 && v[i]==0){
                    //System.out.println("picking "+i);
                    return dfs_p(i, v, g, A);
                }
            }
        }
        return A;
        
    }

    private static double qs(double lo, double hi, Pair[] S) {
        
        double ans = -1.0;
        
        for(int i=0;i<1000;i++){
            double mid = (lo+hi)/2.0;
            //System.out.println("using a radius of "+mid);
            ans=mid;
            long tmp = 0;
            for(int j=0;j<S.length;j++){
                if(mid < S[j].d)    break;
                else{
                    tmp+=Long.parseLong(String.valueOf(S[j].p));
                }
            }
            //System.out.println("pop is "+tmp);
            
            if(tmp >= 1000000){
                hi=mid;
            }
            else if(tmp < 1000000){
                lo=mid;
            }
            
        }
        
       // System.out.println("usig ans os "+ans);
        //check again
        long tmp = 0;
        for(int i=0;i<S.length;i++){
            double d = Double.parseDouble(String.format( "%.7f", S[i].d ));
            ans = Double.parseDouble(String.format( "%.7f", ans ));
            //System.out.println(d+" "+ans);
            if(d > ans)    break;
            else{
                tmp += S[i].p;
            }
        }
        
        if(tmp >= 1000000)  return ans;
        
        
        
        return -1.0;
    }

   

    static class Node{
        
        int d=-1;
        long num;
        public Node(int a,long c){
            this.d = a;
            
            this.num = c;
            
        }
    }
    
    static class Edge{
        
        String d;
        int p;//ids of nodes
        int q;
        public Edge( String x1, int y1, int w){
            
            this.d = x1;
            this.p = y1;
            this.q = w;
        }
    }
    
    //simple sieve
    static boolean[] getPrimes(int n){
        
        boolean[] ret = new boolean[n+1];
        Arrays.fill(ret, true);
        
        ret[0] = ret[1] = false;
        
        for(int i=2;i*i <= n; i++){
            
            if(ret[i]){
                
                for(int j=i*i;j<=n;j+=i){
                    
                    ret[j]=false;
                }
            }
        }
        
        return ret;
    }
   
    static long ibgcd(long a, long b){
        
        while(b > 0){
            long r = a%b;
            a=b;
            b=r;
        }
        return a;
    }
    
    //for extgcd
    static long x,y,d; //output and gdc
    static long c1,c2,a,b,n; // inputs
    //static boolean[] p = getPrimes(5000001);
    
    static class Pair{
        double d ;
        int x;
        int y;
        int p;
        public Pair(int a, int f, int p){
            this.x = a;
            this.y = f;
            this.p=p;
            //compute the radius or euclidean distance
            double r = Math.pow(this.x, 2) + Math.pow(this.y, 2);
            this.d = Math.sqrt(r);
            
        }
    }
    
    static boolean cycle = false;
    
    static Stack<Integer> stack;
    static int[] dfs_low;
    static int[] dfs_num;
    static int timer;
    static int[] visit;
    
    static int[] string_match_basic(String S){
        
        int n = S.length();
        int[] L = new int[n];
        
        int index = 0;
        L[index] = 0; //base case
        
        while(index != n-1){
            
            int d = L[index];
            
            //System.out.println("at "+index+" is "+L[index]);
            
            while(S.charAt(d) != S.charAt(index+1) && d >0){
                d = L[d-1];
            }
            
            L[index+1] = S.charAt(d)==S.charAt(index+1) ? d+1 : 0;
            
            index+=1;
        }
        return L;
    }
    
    
    
    
    
    public static void main(String[] args) throws IOException {
        
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        BufferedWriter bw = new BufferedWriter(new PrintWriter(System.out));
        //Scanner sc = new Scanner(System.in);
  
       
        long n = Long.parseLong(br.readLine());
        n-=2;
        n=(long) Math.pow(n, 2);
        bw.append(n+"\n");
        
        bw.close();
    }
} 