Forth

input/code.cpp: In function 'int main()':
input/code.cpp:27:10: warning: variable 'prod' set but not used [-Wunused-but-set-variable]
   27 |     auto prod = [&]() {
      |          ^~~~
input/code.cpp:33:10: warning: variable 'swapp' set but not used [-Wunused-but-set-variable]
   33 |     auto swapp = [&]() {
      |          ^~~~~
input/code.cpp:43:10: warning: variable 'over' set but not used [-Wunused-but-set-variable]
   43 |     auto over = [&]() {
      |          ^~~~
input/code.cpp:48:10: warning: variable 'rot' set but not used [-Wunused-but-set-variable]
   48 |     auto rot = [&]() {
      |          ^~~

#include <iostream>
#include <tuple>
#include <vector>

using namespace std;

using Z = long long int;

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

    Z x;
    cin >> x;

    vector<const char*> prog;

    vector<Z> sim;
    sim.push_back(1);

    auto plus = [&]() {
        prog.push_back("+");
        if(sim.size() < 2) throw 5;
        sim[sim.size() - 2] += sim.back();
        sim.pop_back();
    };
    auto prod = [&]() {
        prog.push_back("*");
        if(sim.size() < 2) throw 5;
        sim[sim.size() - 2] *= sim.back();
        sim.pop_back();
    };
    auto swapp = [&]() {
        prog.push_back("SWAP");
        if(sim.size() < 2) throw 5;
        swap(sim[sim.size() - 2], sim.back());
    };
    auto dup = [&]() {
        prog.push_back("DUP");
        if(sim.empty()) throw 5;
        sim.push_back(sim.back());
    };
    auto over = [&]() {
        prog.push_back("OVER");
        if(sim.size() < 2) throw 5;
        sim.push_back(sim[sim.size() - 2]);
    };
    auto rot = [&]() {
        prog.push_back("ROT");
        if(sim.size() < 3) throw 5;
        tie(sim[sim.size() - 3], sim[sim.size() - 2], sim[sim.size() - 1])
            = tuple(sim[sim.size() - 2], sim[sim.size() - 1], sim[sim.size() - 3]);
    };
    auto drop = [&]() {
        prog.push_back("DROP");
        if(sim.empty()) throw 5;
        sim.pop_back();
    };

    if(x == 1) {
        dup();
        drop();
    } else {
        Z p = 1;
        while(2 * p <= x) {
            if(x & p) {
                dup();
            }
            dup();
            plus();
            p *= 2;
        }

        while(sim.size() > 1) {
            plus();
        }
    }

    if(sim.empty() || sim.size() != 1 || sim.back() != x) {
        cerr << "INCORRECT " << sim.size() << " " << sim.back() << "\n";
        throw 5;
    }

    cout << prog.size() << "\n";
    for(const char* step : prog) {
        cout << step << " ";
    }
    cout << "\n";

    return 0;
}

Test 1

Verdict: ACCEPTED

Test 2

Verdict: ACCEPTED

Test 3

Verdict: ACCEPTED

Test 4

Verdict: ACCEPTED

Test 5

Verdict: ACCEPTED

Test 6

Verdict: ACCEPTED

Test 7

Verdict: ACCEPTED

Test 8

Verdict: ACCEPTED

Test 9

Verdict: ACCEPTED

Test 10

Verdict: ACCEPTED

Test 11

Verdict: ACCEPTED

Test 12

Verdict: ACCEPTED

Test 13

Verdict: ACCEPTED