at() Throws, [] Does Not Check

1#include <iostream>
2#include <stdexcept>
3#include <vector>
4 
5int main() {
6    std::vector<int> scores = {70, 85, 90};
7    int positions[] = {0, 2, 3, 1};
8    for (int pos : positions) {
9        try {
10            int value = scores.at(pos);
11            std::cout << "position " << pos << ": " << value << "\n";
12        } catch (const std::out_of_range&) {
13            std::cout << "position " << pos << " is outside the vector\n";
14        }
15    }
16    std::cout << "size " << scores.size() << "\n";
17    return 0;
18}