import java.util.*;
public class Main {
public static void main(String args[]) {
// Your Code Here
Scanner scn=new Scanner(System.in);
int n=scn.nextInt();
int arr[]=new int[n];
for(int i=0;i<n;i++){
arr[i]=i+1;
}
System.out.println(sum(arr,arr.length-1));
}
public static int sum(int arr[],int idx){
if(idx<0){
return 0;
}
int sum=arr[idx]+sum(arr,idx-2);
return sum;
}
}
it is given in the input that the ith index will be the value of ith coin so according to this our array will be sorted from 1 to n like we have the example of n=4 so the respective array will be 1,2,3,4 and according if Piyush wants to win he should always pick the coin or element from array last index and the index must always decrease by 2 because another guy also want to win .
