#include <iostream>
using namespace std;
int main() {
long long n;
cin>>n;
long long r=0;
if (n%2==0){
r=n/2;
}
else{
r=-(n/2+1);
}
cout<<r;
return 0;
}
I2luY2x1ZGUgPGlvc3RyZWFtPgp1c2luZyBuYW1lc3BhY2Ugc3RkOwoKaW50IG1haW4oKSB7Cglsb25nIGxvbmcgbjsKCWNpbj4+bjsKCWxvbmcgbG9uZyByPTA7CglpZiAobiUyPT0wKXsKCQlyPW4vMjsKCX0KCWVsc2V7CgkJcj0tKG4vMisxKTsKCX0KCWNvdXQ8PHI7CglyZXR1cm4gMDsKfQ==