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25 lines
411 B
C++
25 lines
411 B
C++
#include <bits/stdc++.h>
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using namespace std;
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int n, t, a[200005];
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int main() {
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set<int> s;
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cin >> n;
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for (int i = 0; i < n; i++) {
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cin >> t;
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s.insert(t);
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}
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if (s.size() <= 1) {
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cout << -1 << endl;
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} else {
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t = 0;
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for (int i : s) {
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a[++t] = i;
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}
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cout << max(a[t - 2], a[t] % a[t - 1]) << endl;
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}
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return 0;
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}
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