diff --git a/day 17/day_17_max_n.cpp b/day 17/day_17_max_n.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..93390003dce59e20fe74bcf93bd93537d8a72c46
--- /dev/null
+++ b/day 17/day_17_max_n.cpp
@@ -0,0 +1,204 @@
+#include <bits/stdc++.h>
+
+#ifdef LOCAL
+#include "./cpp-dump/cpp-dump.hpp"
+#define pr(x) cpp_dump(x)
+#endif
+
+using namespace std;
+
+#define Mod(x,y) (((x)%(y)+(y))%(y))
+#define rep(i, a, b) for(ll (i) = (a); (i) < (b); ++(i))
+#define all(x) begin(x), end(x)
+#define pb push_back
+#define gcd __gcd
+#define sz(x) (ll)(x.size())
+
+typedef long long ll;
+typedef unsigned long long ull;
+typedef pair<ll, ll> pii;
+typedef vector<ll> vi;
+typedef vector<pii> vii;
+
+const bool debug = false;
+
+vector<ll> reg = {0, 0, 0};
+vector<ll> output, A_bin;
+
+ll pointer = 0;
+
+ll get_operand(ll x) {
+ if (x >= 0 && x <= 3) return x;
+ if (x >= 4 && x <= 6) return reg[x-4];
+ assert(false);
+ return 0;
+}
+
+ll instruction(ll opcode, ll x) {
+ ll res = LLONG_MAX;
+ bool ok = true;
+ ll combo = get_operand(x);
+ if (opcode == 0) {
+ ll num = reg[0];
+ ll den = 1;
+ rep(i, 0, combo) {
+ den *= 2;
+ if (den > num) break;
+ }
+ reg[0] = num/den;
+ } else if (opcode == 1) {
+ reg[1] = reg[1]^x;
+ } else if (opcode == 2) {
+ reg[1] = Mod(combo, 8);
+ } else if (opcode == 3) {
+ if (reg[0] != 0) {
+ ok = false;
+ pointer = x;
+ }
+ } else if (opcode == 4) {
+ reg[1] = reg[1]^reg[2];
+ } else if (opcode == 5) {
+ res = Mod(combo, 8);
+ output.pb(res);
+ } else if (opcode == 6) {
+ ll num = reg[0];
+ ll den = 1;
+ rep(i, 0, combo) {
+ den *= 2;
+ if (den > num) break;
+ }
+ reg[1] = num/den;
+ } else if (opcode == 7) {
+ ll num = reg[0];
+ ll den = 1;
+ rep(i, 0, combo) {
+ den *= 2;
+ if (den > num) break;
+ }
+ reg[2] = num/den;
+ }
+
+ if (ok) pointer+=2;
+ return res;
+}
+
+bool same(vector<ll> instructions, ll A) {
+ reg[0] = reg[1] = reg[2] = 0;
+ reg[0] = A;
+ output.clear();
+ pointer = 0;
+ int ind = 0;
+ while(pointer < instructions.size()) {
+ if (debug) {
+ pr(instructions[pointer]);
+ pr(instructions[pointer+1]);
+ }
+ ll res = instruction(instructions[pointer], instructions[pointer+1]);
+ if (debug) pr(reg);
+
+ if (instructions.size() < output.size()) return false;
+ if (res < LLONG_MAX) {
+ if (instructions[ind] != res) return false;
+ ind++;
+ }
+ }
+
+ if (instructions.size() != output.size()) return false;
+ rep(i, 0, sz(instructions)) if (instructions[i] != output[i]) return false;
+
+ return true;
+}
+
+vi generate(int a_3, int a_2, int a_1) {
+ vector<int> a3s, a2s, a1s;
+ if (a_3 == -1) a3s = {0, 1};
+ else a3s = {a_3};
+ if (a_2 == -1) a2s = {0, 1};
+ else a2s = {a_2};
+ if (a_1 == -1) a1s = {0, 1};
+ else a1s = {a_1};
+
+ vi res;
+ for (int a3 : a3s) for (int a2 : a2s) for (int a1 : a1s) res.pb(4*a3 + 2*a2 + a1);
+ return res;
+}
+
+vi to_bin(int x) {
+ vi res = {(x>>2)&1, (x>>1)&1, x&1};
+ return res;
+}
+
+bool valid(int ptr, int x) {
+ rep(i, 0, 3) if (A_bin[ptr-i] != -1 && A_bin[ptr-i] != to_bin(x)[i]) return false;
+ return true;
+}
+
+ll get_ans() {
+ int i = 127;
+ ll ans = 0;
+ while(A_bin[i] != 1) {
+ i--;
+ }
+ while(i >= 0) {
+ ans = 2*ans + (A_bin[i] == 1 ? 1 : 0);
+ i--;
+ }
+ return ans;
+}
+
+vector<ll> instructions;
+bool pos(int instruction_ind) {
+ if (instruction_ind == sz(instructions)) {
+ return same(instructions, get_ans());
+ }
+ bool res = false;
+ int ptr = 3*instruction_ind+2;
+ int a_3 = A_bin[ptr], a_2 = A_bin[ptr-1], a_1 = A_bin[ptr-2];
+ int v0 = instructions[instruction_ind];
+ vi minus_ones_pre;
+ rep(i, 0, 3) if (A_bin[ptr-i] == -1) minus_ones_pre.pb(i);
+
+ for (int a : generate(a_3, a_2, a_1)) {
+ A_bin[ptr] = to_bin(a)[0];
+ A_bin[ptr-1] = to_bin(a)[1];
+ A_bin[ptr-2] = to_bin(a)[2];
+
+ int X = v0^(a^6);
+
+ int new_ptr = ptr+(a^3);
+
+ if (valid(new_ptr, X)) {
+ vi minus_ones;
+ rep(i, 0, 3) if (A_bin[new_ptr-i] == -1) minus_ones.pb(i);
+ rep(i, 0, 3) if (A_bin[new_ptr-i] = to_bin(X)[i]);
+
+ if (pos(instruction_ind+1)) return true;
+ for (int i : minus_ones) A_bin[new_ptr-i] = -1;
+ }
+ }
+ for (int i : minus_ones_pre) A_bin[ptr-i] = -1;
+ return false;
+}
+
+void solve() {
+ cin >> reg[0] >> reg[1] >> reg[2];
+ ll x;
+ while(cin >> x) instructions.pb(x);
+
+ rep(i, 0, 128) A_bin.pb(-1);
+ bool ok = pos(0);
+ ll ans = get_ans();
+ pr(ans);
+}
+
+
+int main() {
+ ios::sync_with_stdio(0);cin.tie(0);
+ cout << setprecision(15) << fixed;
+
+#ifdef LOCAL
+ freopen("input.txt", "r", stdin);
+#endif
+
+ solve();
+}