#include<stdio.h>

int n,nr,i;

int main(){

 FILE *f=fopen("nunta.in","r");


fscanf(f,"%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");
   fprintf(g,"%d",nr);
   fclose(f);



return 0;
}