Codeforces Round #242 (Div. 2) C Magic Formulas

 1 #include <iostream>
 2 #include <stdio.h>
 3 #include <string.h>
 4 using namespace std;
 5 int array[1000001];
 6 int main(){
 7     int cnt, i, j, k, t, n, num;
 8     int temp = 0;
 9     for(k = 0 ;k <= 1000000 ; k++){
10         temp ^= k;
11         array[k] = temp;
12     }
13     while(EOF != scanf("%d",&n)){
14         cnt = 0;
15         for(i = 1; i <= n; i++){
16             scanf("%d",&num);
17             cnt ^= num;
18         }
19         for(i = 1 ;i <= n; i++){
20             int tmp_q = n / i;
21             int tmp_w = n % i;
22             while(tmp_q--){
23                 cnt ^= array[i-1];
24             }
25             if(tmp_w)
26                 cnt ^= array[tmp_w];
27         }
28         printf("%d\n",cnt);
29     }
30     return 0;
31 }