#include<iostream> // cin\cout\endl #include<cstdio> //scanf()\printf() #include<cstring> // strcpy()\strcat()\strcmp()\strlen()\memset() #include<cmath> //sqrt()\pow()\abs()\ceil()\floor()\max()\min() using namespace std; int main(){ int n; cin>>n; if((n-1)%2==0) { cout<<1-(n-1)/2*1;} else{ cout<<1-(n-2)/2*1+n; } return 0; }