Day 18 part 1, using C++ compiler

#include <iostream>
#include <vector>

struct N {
    N(int64_t v) : v(v) {}
    int64_t v;
};

N operator+(N a, N b) { return { a.v + b.v }; }
N operator-(N a, N b) { return { a.v * b.v }; }

extern std::vector<N> values;

int main() {
    int64_t sum = 0;
    for (auto& value : values) {
        sum += value.v;
    }
    std::cout << sum << std::endl;
}

// Process your input like this:
// sed -E 's/[0-9]+/N(\0)/g ; s/\*/-/g ; s/$/,/' input