CodeForce 424C Magic Formulas

这个题就是求出给的公式的结果。

仅仅要知道异或运算满足交换律跟结合律即可了。之后就是化简公式。

#include<map>
#include<string>
#include<cstring>
#include<cstdio>
#include<cstdlib>
#include<cmath>
#include<queue>
#include<vector>
#include<iostream>
#include<algorithm>
#include<bitset>
#include<climits>
#include<list>
#include<iomanip>
#include<stack>
#include<set>
using namespace std;
int psum[1000010];
int main()
{
	int n;
	cin>>n;
	int ans=0;
	for(int i=0;i<n;i++)
	{
		int t;
		scanf("%d",&t);
		ans^=t;
	}
	for(int i=1;i<n;i++)
		psum[i]=i^psum[i-1];
	for(int i=1;i<=n;i++)
	{
		int t=n/i;
		if(t&1)
			ans^=psum[i-1];
		t=n%i;
		ans^=psum[t];
	}
	cout<<ans;
}

Magic Formulas

time limit per test

2 seconds

memory limit per test

256 megabytes

input

standard input

output

standard output

People in the Tomskaya region like magic formulas very much. You can see some of them below.

Imagine you are given a sequence of positive integer numbers p1, p2,
..., pn.
Lets write down some magic formulas:

Here, "mod" means the operation of taking the residue after dividing.

The expression  means
applying the bitwise xor (excluding "OR") operation to integers x and y.
The given operation exists in all modern programming languages. For example, in languages C++ and Java it is represented by "^", in Pascal — by
"xor".

People in the Tomskaya region like magic formulas very much, but they don't like to calculate them! Therefore you are given the sequence p,
calculate the value of Q.

Input

The first line of the input contains the only integer n (1 ≤ n ≤ 106).
The next line contains n integers: p1, p2, ..., pn (0 ≤ pi ≤ 2·109).

Output

The only line of output should contain a single integer — the value of Q.

Sample test(s)

input

3
1 2 3

output

3