#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 i,n,s=10000; cin>>n; for(i=3;i>=n;i=-1){ s=s+(i-2); } cout<<s; return 0; }