#include <stdio.h>
#include <math.h>

int n;

int main()
{

    for(int p = 1 ; p <= 30 ; p++ )
    {
        char in[100], out[100];
        sprintf(in, ".%d.in", p);
        sprintf(out, ".%d.out", p);
        freopen(in, "r",stdin);
        freopen(out, "w", stdout);
        int sum=0;


        scanf("%d", &n);

        if((int)ceil(n/2.0)%2==0)
        {
            for(int i=1; i<=n; i++)
                if(i%2==1) sum+=i;
        }
        else
        {
            for(int i=1; i<=n; i++)
                if(i%2==0) sum+=i;
        }

        printf("%d", sum);
    }
}