Forth

#include <iostream>
#include <string>
#include <vector>
using namespace std;

int main() {
    cin.tie(0)->sync_with_stdio(0);
    int x; cin>>x;

    vector<int> S{1};
    vector<string> ans{"DUP", "*"};
    while (S.back() < x) {
        ans.push_back("DUP");
        ans.push_back("DUP");
        ans.push_back("+");
        S.push_back(S.back() + S.back());
    }
    while (S.size() > 1) {
        if (S.back() > x) {
            S.pop_back();
            ans.push_back("DROP");
        }
        else if (S[S.size()-1] + S[S.size()-2] > x) {
            swap(S[S.size()-1], S[S.size()-2]);
            S.pop_back();
            ans.push_back("SWAP");
            ans.push_back("DROP");
        }
        else {
            S[S.size()-2] += S[S.size()-1];
            S.pop_back();
            ans.push_back("+");
        }
    }

    cout << ans.size() << '\n';
    for (int i=0, n=ans.size(); i<n; i++) {
        cout << ans[i] << " \n"[i+1==n];
    }
}

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