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  1. #include<bits/stdc++.h>
  2. #pragma GCC optimize("Ofast")
  3. #pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
  4. using namespace std;
  5. #define int long long
  6. //#define int unsigned long long
  7. //define int __int128
  8. #define all(x) x.begin(),x.end()
  9. #define pb push_back
  10. #define pf push_front
  11. #define rall(x) x.rbegin(),x.rend()
  12. const int N=1e6+7,mod=998244353,MOD=1000000007,dom=0,inf=2147483647;//,INF=9223372036854775807;
  13. int n,a[N],x,cnt[N],ans=0;
  14. void solve(int TCS){
  15.     cin>>n;
  16.     for(int i=2;i<=n;i++){
  17.         x=n/i;
  18.         cnt[0]+=x,cnt[i]-=x;
  19.         if(n%i!=0){
  20.             cnt[1]++,cnt[n%i+1]--;
  21.         }
  22.     }
  23.     for(int i=1;i<n;i++){
  24.         cnt[i]+=cnt[i-1];
  25.     }
  26.     for(int i=1;i<=n;i++){
  27.         cin>>a[i];
  28.         ans^=a[i];
  29.     }
  30.     for(int i=1;i<n;i++){
  31.         if(cnt[i]%2!=0){
  32.             ans^=i;
  33.         }
  34.     }
  35.     cout<<ans;
  36. }
  37. signed main(){
  38.     ios::sync_with_stdio(false);
  39.     cin.tie(NULL);
  40.     //freopen("input.txt","r",stdin);
  41.     //freopen("output.txt","w",stdout);
  42.     int T=1;
  43.     //cin>>T;
  44.     for(int TCS=1;TCS<=T;TCS++){
  45.         solve(TCS);
  46.     }
  47. }
  48. //Bismillah
  49. //33 Subhanallah
  50. //33 Alhamdulillah
  51. //33 Allahu Akbar
  52. /*
  53.  
  54. */
  55.  
Success #stdin #stdout 0.01s 5256KB
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https://ideone.com/97S1Cy
language:
C++ (gcc 8.3)
created:
4 hours ago
visibility:
secret

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