#include <bits/stdc++.h> using namespace std; const int maxn = 1e6+10; int a[maxn]; int v[maxn]; int busca1(int l, int r, int pos, int x) { int ini = l, fim = r, ans = -1; while (ini <= fim) { int mid = (ini+fim)>>1; if (a[mid] + a[pos] <= x) ans = mid, ini = mid+1; else fim = mid-1; } return ans; } int busca2(int l, int r, int pos, int x) { int ini = l, fim = r, ans = -1; while (ini <= fim) { int mid = (ini+fim)>>1; if (a[mid] + a[pos] >= x) ans = mid, fim = mid-1; else ini = mid+1; } return ans; } int main(void) { int n; scanf("%d", &n); for (int i = 1; i <= n; i++) scanf("%d", &v[i]); int ans = 0; for (int b = 0; b <= 30; b++) { int qtd = 0; for (int i = 1; i <= n; i++) a[i] = v[i]%(1<<(b+1)); sort(a+1, a+n+1); for (int i = 1; i <= n; i++) { int l = busca2(1, i, i, (1<<b)); int r = busca1(1, i, i, (1<<(b+1))-1); if (l != -1 && r != -1) qtd += (r-l+1); l = busca2(1, i, i, (1<<b) + (1<<(b+1))); r = busca1(1, i, i, (1<<(b+2))-2); if (l != -1 && r != -1) qtd += (r-l+1); } if (qtd%2) ans += (1<<b); } printf("%d\n", ans); }

xorsum.cpp: In function 'int main()':
xorsum.cpp:43:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d", &n);
  ~~~~~^~~~~~~~~~
xorsum.cpp:46:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d", &v[i]);
   ~~~~~^~~~~~~~~~~~~