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22 lines
376 B
22 lines
376 B
2 years ago
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#include <bits/stdc++.h>
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using namespace std;
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const int N = 10010;
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int L, m;
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bool st[N];
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int main() {
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cin >> L >> m;
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while (m--) {
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int l, r;
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cin >> l >> r;
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for (int i = l; i <= r; i++) st[i] = 1;
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}
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int res = 0;
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for (int i = 0; i <= L; i++)
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if (!st[i]) res++;
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printf("%d\n", res);
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return 0;
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}
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