#include <stdio.h>

int main() {
    int n,s=0,t=1,i;
    scanf("%d",&n);
    for(i=1;i<=n;n++)
    {
        if(n%2==0)
        s=-n/2;//1-2+3-4=-2
        else
        s=(n+1)/2;
        break;
    }
    printf("%d\n",s);
    return 0;
}