#include<stdio.h>
int n,nr,i;
int main(){
 FILE *f=fopen("nunta.in","r");
scanf("%d",&n);
fclose(f);
nr=1;
   for(i=1;i<=n/2;i++)
   nr=nr+(n-i*2+1);
FILE *g=fopen("nunta.out","w");
printf("%d",nr);
fclose(f);

return 0;
}