POJ-2081

#include<iostream>#include<memory.h>using namespace std;#define MAX_K 500000int main(int argc, char *argv[]){int v[MAX_K+1];bool hash[3012501];memset(hash,false,sizeof(hash));int aM_1=0;v[0]=aM_1;hash[0]=true;for(int i=1;i<=MAX_K;i++){int aM=aM_1-i;if(aM<=0 || hash[aM]){aM=aM_1+i;}v[i]=aM;hash[aM]=true;aM_1=aM;}int k;while(cin>>k,k!=-1){cout<<v[k]<<endl;}return 0;}