poj 2081

#include<cstdio>#include<cstring>bool vis[10000000];int  a[500050];void init(){memset(vis,0,sizeof(vis));a[0]=0;for(int i=1;i<=500000;i++){if(!vis[a[i-1]-i]&&a[i-1]-i>0)a[i]=a[i-1]-i;elsea[i]=a[i-1]+i;vis[a[i]]=1;}}int main(){int x;init();while(~scanf("%d",&x)&&(x!=-1))printf("%d\n",a[x]);}