diff --git a/day17.py b/day17.py
new file mode 100644
index 0000000..318dbba
--- /dev/null
+++ b/day17.py
@@ -0,0 +1,185 @@
+#!/usr/bin/env python3
+
+import re
+from random import randrange
+from array import array
+from copy import copy
+
+class VM():
+    def __init__(self, reg: array = array('q'), mem: list = [], pc: int = 0):
+        self.reg = copy(reg)
+        self.mem = copy(mem)
+        self.pc = copy(pc)
+        self.outbuf = []
+
+    def _combo(self, c) -> int:
+        if c == 0: return 0
+        if c == 1: return 1
+        if c == 2: return 2
+        if c == 3: return 3
+        if c == 4: return self.reg[0]
+        if c == 5: return self.reg[1]
+        if c == 6: return self.reg[2]
+        raise RuntimeError()
+
+    def run(self, abort: int = 0):
+        while self.pc < len(self.mem):
+            if abort>0 and len(self.mem) > abort: return
+
+            op = self.mem[self.pc]
+            self.pc += 1
+
+            if op == 0b000: # adv
+                self.reg[0] = self.reg[0] // (2**self._combo(self.mem[self.pc]))
+                self.pc += 1
+            if op == 0b001: # bxl
+                self.reg[1] = self.reg[1] ^ self.mem[self.pc]
+                self.pc += 1
+            if op == 0b010: # bst
+                self.reg[1] = self._combo(self.mem[self.pc]) & 0b111
+                self.pc += 1
+            if op == 0b011: # jnz
+                self.pc = self.mem[self.pc] if self.reg[0] != 0 else self.pc+1
+            if op == 0b100: # bxc
+                self.reg[1] = self.reg[1] ^ self.reg[2]
+                self.pc += 1
+            if op == 0b101: # out
+                self.outbuf.append(self._combo(self.mem[self.pc]) & 0b111)
+                self.pc += 1
+            if op == 0b110: # bdv
+                self.reg[1] = self.reg[0] // (2**self._combo(self.mem[self.pc]))
+                self.pc += 1
+            if op == 0b111: # cdv
+                self.reg[2] = self.reg[0] // (2**self._combo(self.mem[self.pc]))
+                self.pc += 1
+
+
+    def flush(self, binfmt = False):
+        if not binfmt:
+            print(','.join(map(str, self.outbuf)))
+        else:
+            for o in self.outbuf:
+                print(f"{o:b},", end="")
+            print()
+
+    def cmp(self, prog):
+        return self.outbuf == prog
+
+
+reg: array = array('q')
+mem: list = []
+pc: int = 0
+
+with open('day17') as f:
+    reg_a = int(re.match('Register A: ([0-9]+)', f.readline()).groups()[0])
+    reg_b = int(re.match('Register B: ([0-9]+)', f.readline()).groups()[0])
+    reg_c = int(re.match('Register C: ([0-9]+)', f.readline()).groups()[0])
+
+    reg = array('q', [reg_a, reg_b, reg_c])
+
+    f.readline()
+
+    mem_str = re.match('Program: (.*)', f.readline()).groups()[0]
+
+    for c in mem_str:
+        if c == ',': continue
+        mem.append(int(c))
+
+vm = VM(reg, mem, pc)
+vm.run()
+vm.flush()
+
+# enumerates all 3 bit number, then increases size by one
+# enumerates them again
+#
+# don't know how exactly it enumerates but it enumerate
+# lower bytes before changing high byte
+# -> we can tighten boundaries ever more once we find
+# valid high bytes one after the other
+#
+# but first we need to find where to even start
+# we know the reg_a from the puzzle input is
+# too small, but start from here and increas rapidly:
+
+reg_a = 17323786
+while True:
+    reg = array('q', [reg_a, reg_b, reg_c])
+    vm = VM(reg, mem, pc)
+    vm.run(abort=len(mem))
+    if vm.cmp(mem): break
+
+    # if reg_a % 1 == 0:
+    #     vm.flush(binfmt=True)
+
+    if len(mem) == len(vm.outbuf): break
+
+    reg_a *= 10
+
+
+print(reg_a)
+vm.flush()
+
+# well that was fast
+# we get: 173237860000000
+# producing a program: 4,4,4,4,1,6,0,0,0,2,1,0,0,1,3,0
+#
+# that's long enough and even better we even got the 2 highest bytes right
+# already
+
+
+# let's find our first set of boundaries so we can start a binary search
+known_bytes = vm.outbuf[-2:]
+init_reg_a = reg_a
+upper_bound = -1
+lower_bound = -1
+
+reg_a = init_reg_a
+while True:
+    reg = array('q', [reg_a, reg_b, reg_c])
+    vm = VM(reg, mem, pc)
+    vm.run(abort=len(mem))
+    if vm.cmp(mem): break
+
+    if vm.outbuf[-2:] != known_bytes:
+        upper_bound = reg_a
+        break
+
+    if len(vm.outbuf) > len(mem):
+        upper_bound = reg_a
+        break
+
+    reg_a *= 10
+
+
+print(reg_a)
+vm.flush()
+
+reg_a = init_reg_a
+while True:
+    reg = array('q', [reg_a, reg_b, reg_c])
+    vm = VM(reg, mem, pc)
+    vm.run(abort=len(mem))
+    if vm.cmp(mem): break
+
+    if vm.outbuf[-2:] != known_bytes:
+        lower_bound = reg_a
+        break
+
+    if len(vm.outbuf) < len(mem):
+        lower_bound = reg_a
+        break
+
+    reg_a //= 10
+
+
+print(reg_a)
+vm.flush()
+
+
+# that was fast again and did not produce very enlightening bounds,
+# nevertheless we have bounds
+#
+# ub: 1732378600000000
+# out: 4,4,0,7,0,7,6,0,3,5,1,5,4,2,4,4,2
+# lb: 17323786000000
+# 4,4,5,5,5,0,1,4,6,4,4,4,7,3,7