main.cpp:982:5: error: conflicting declaration of C function 'int main(int, char**)'
  982 | int main(int argc, char** argv) {
      |     ^~~~
In file included from main.cpp:4:
solution.cpp:27:5: note: previous declaration 'int main()'
   27 | int main() {
      |     ^~~~

// g++ -std=c++17 a.cpp -o a; ./a

#include <iostream>
#include <vector>
#include <string>

using namespace std;

#define ll long long

const int INF = 1e9;
const ll LINF = 1e18;

class ValueAddedTax {
    public:
        double calculateFinalPrice(string product, int price, vector<string> food)
        {
            for (int i=0;i<food.size();i++) {
                if (product == food[i]) {
                    return (double) price + (double)price*0.1;
                }
            }
            return (double) price + (double)price*0.18;
        }
};

int main() {
    ValueAddedTax a;
    cout<<a.calculateFinalPrice("milk", 1, {"bread", "butter", "milk"})<<endl;
}