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33 lines
581 B
C++
33 lines
581 B
C++
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#include <iostream>
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using std::cin;
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using std::cout;
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const char endl = '\n';
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const int N = 1e7 + 5;
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long long l, r, k, ans;
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int cnt, primes[N];
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bool vis[N];
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int main() {
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std::ios::sync_with_stdio(false);
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cin.tie(nullptr);
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cin >> l >> r >> k;
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for (long long i = 2; i * i <= r && i <= k; i++) {
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for (long long j = std::max(((l + i - 1) / i) * i, i * 2); j <= r; j += i) {
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vis[j - l + 1] = true;
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}
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}
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for (long long i = l; i <= r; i++) {
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if (!vis[i - l + 1]) ans ^= i;
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}
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cout << ans << endl;
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return 0;
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}
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