[51nod] 2653 section XOR

Section xor

Link

---

Their thinking

code

#include<iostream>
#include<cstdio>
using namespace std;

int a,b;

int f(int x)
{
    
	if(x%4==1) return 0;
	if(x%4==3) return 1;
	return f(x-1)^x;
}

int main()
{
    
	cin>>a>>b;
	printf("%d\n",f(b)^f(a-1));
}