25 lines
555 B
C++
25 lines
555 B
C++
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#include <iostream>
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#include <vector>
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#include <algorithm>
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using namespace std;
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int main() {
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int k;
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cin >> k;
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vector<int> arr;
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for (int i = 0; i < k; i++) {
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int t;
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cin >> t;
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arr.push_back(t);
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}
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auto ptr = unique(arr.begin(), arr.end());
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arr.erase(ptr, arr.end());
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if (arr.size() <= 2) {
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cout << -1 << endl;
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return 0;
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}
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sort(arr.begin(), arr.end());
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arr.insert(arr.begin(), 1, 0);
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auto kp = arr.size()-1;
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cout << max(arr[kp - 2], arr[kp] % arr[kp - 1]) << endl;
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}
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