#include<iostream>
using namespace std;
int answer[500000]={0};
bool b[3100000]={0};
void slove(int k)
{
    if(answer[k]) return;
    else {
         if(answer[k-1]-k<=0||(answer[k-1]-k>=0&&b[answer[k-1]-k])) {answer[k]=answer[k-1]+k;}
         else answer[k]=answer[k-1]-k;
         }
    b[answer[k]]=1;
}
int main()
{   
    int s[1000],count=0;
    answer[0]=0;b[0]=1;
    while(1)
    {
    int k,start=0;
    cin>>k;
    if(k==-1) break;
    for(int i=k;i>=0;i--)
     if(answer[i]) start=i;
    for(int j=start;j<=k;j++)
     slove(j);
    s[count++]=answer[k];
    }
    for(int h=0;h<count;h++)
     cout<<s[h]<<endl;
    return 0;
}