Codeforces Round #242 (Div. 2)C(找规律，异或运算)

#include<iostream>
#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
#include<map>
#include<set>
#include<vector>
#include<algorithm>
#include<stack>
#include<queue>
using namespace std;
#define INF 1000000000
#define eps 1e-8
#define pii pair<int,int>
#define LL long long int
int n,p;
int ans=0;
int x[1000009];
int main()
{
    //freopen("in7.txt","r",stdin);
    //freopen("out.txt","w",stdout);
    scanf("%d",&n);
    x[0]=0;
    for(int i=1; i<=n; i++)
    {
        x[i]=x[i-1]^(i-1);
        int t=n/i;
        if(t%2==1)      ans^=x[i];
        ans^=x[n%i+1];
    }
    for(int i=0; i<n; i++)
    {
        scanf("%d",&p);
        ans^=p;
    }
    printf("%d\n",ans);
    //fclose(stdin);
    //fclose(stdout);
    return 0;
}