The code below is provided in the guide.

Can someone please provide an explanation for the significance of **function<bool(int**)> f in **last_true** function

```
#include <bits/stdc++.h>
using namespace std;
int last_true(int lo, int hi, function<bool(int)> f) {
lo--;
while (lo < hi) {
int mid = lo + (hi - lo + 1) / 2;
if (f(mid)) {
lo = mid;
} else {
hi = mid - 1;
}
}
return lo;
}
int main() {
int size;
int max_ops;
cin >> size >> max_ops;
vector<int> arr(size);
for (int &i : arr) { cin >> i; }
sort(arr.begin(), arr.end());
// Use 2e9 instead of INT32_MAX to avoid overflow
cout << last_true(1, 2e9, [&](int x) {
// Returns true if the median can be raised to x
long long ops_needed = 0;
for (int i = (size - 1) / 2; i < size; i++) {
ops_needed += max(0, x - arr[i]);
}
return ops_needed <= max_ops;
}) << endl;
}
```