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// Integer binary search
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int L = 0, R = 1e9;
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int ans = -1;
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while (L <= R) {
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    int mid = (L + R) >> 1;
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    if (check(mid)) {
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        ans = mid;
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        R = mid - 1;
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    } else {
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        L = mid + 1;
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    }
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}
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// Real number binary search or floating-point binary search
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long double l = 0, r = 1e9;
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int T = 100;
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while (T--) {
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    long double mid = (l + r) * 0.5;
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    if (check(mid)) {
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        l = mid;
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    } else {
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        r = mid;
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    }
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}
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cout << l << "\n"; // Outputting 'r' is also acceptable
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// Binary search functions
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// lower_bound(*begin, *end, val, cmp) // cmp is a custom comparison function (optional, not recommended to use)
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// upper_bound()
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// lower_bound: Under the given sorting rule, finds the first pointer to a value greater than or equal to 'val'
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// upper_bound: Under the given sorting rule, finds the first pointer to a value greater than 'val'
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// Example:
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int a[50];
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a[1] = 2;
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a[2] = 4;
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a[3] = 5;
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a[4] = 6;
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auto it = lower_bound(a + 1, a + 49, 5);
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cout << *it << "\n"; // Outputs 5 (a[3]), actually obtains the position of the first value greater than or equal to the required value (val = 5)
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// Access the first value greater than or equal to 'val'
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// Second usage method:
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int pos = lower_bound(a + 1, a + 49, 5) - a; // Obtains the desired position
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// a[pos] == *it