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36 lines
708 B
36 lines
708 B
#include <bits/stdc++.h>
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using namespace std;
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const int N = 110;
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struct Node {
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int st;
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int ed;
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} seg[N];
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bool cmp(Node a, Node b) {
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if (a.st == b.st) return a.ed < b.ed;
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return a.st < b.st;
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}
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int m, L;
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int main() {
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cin >> L >> m;
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for (int i = 0; i < m; i++) cin >> seg[i].st >> seg[i].ed;
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sort(seg, seg + m, cmp);
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int res = L + 1;
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int st = seg[0].st, ed = seg[0].ed;
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for (int i = 1; i < m; i++)
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if (seg[i].st <= ed)
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ed = max(seg[i].ed, ed);
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else {
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res -= ed - st + 1;
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st = seg[i].st, ed = seg[i].ed;
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}
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res -= ed - st + 1;
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cout << res << endl;
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return 0;
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} |