#include<stdio.h>

int main()

{
    int x,a,b;

    scanf("%d",&x);

    if(x%2!=0)
    {
        a=x/2;
        b=(x/2)+1;
    }
    else
    {
        a=x/2;
        b=x/2;
    }

    printf("%d\n",a*b);
    return 0;
}
