Binge watching

input/code.cpp: In function 'int main()':
input/code.cpp:17:19: error: 'a' was not declared in this scope
   17 |     std::cout << (a + b) << std::endl;
      |                   ^
input/code.cpp:17:23: error: 'b' was not declared in this scope
   17 |     std::cout << (a + b) << std::endl;
      |                       ^

#include <bits/stdc++.h>

int main() {
    std::ios_base::sync_with_stdio(false);
    std::cin.tie(nullptr);

    long long n;
    std::cin >> n;

    std::vector<int> widths(n+1);
    for (int i = 0; i < n; i++) {
        int w;
        std::cin >> w;
        widths[i] = w;
    }

    std::cout << (a + b) << std::endl;
    return 0;
}