diff --git a/day17/input b/day17/input
new file mode 100644
index 0000000..b706a5d
--- /dev/null
+++ b/day17/input
@@ -0,0 +1,5 @@
+Register A: 46337277
+Register B: 0
+Register C: 0
+
+Program: 2,4,1,1,7,5,4,4,1,4,0,3,5,5,3,0
diff --git a/day17/sol.py b/day17/sol.py
new file mode 100644
index 0000000..4cc506c
--- /dev/null
+++ b/day17/sol.py
@@ -0,0 +1,56 @@
+
+sample = [0,1,5,4,3,0]
+input = [2,4,1,1,7,5,4,4,1,4,0,3,5,5,3,0]
+
+def simulate(a, prog, check=False):
+    b = 0
+    c = 0
+    ip = 0
+
+    out = []
+
+    while ip < len(prog):
+        op = prog[ip]
+        r = prog[ip+1]
+
+        if op in (0,2,5,6,7):
+            # combo op
+            if r == 4:
+                r = a
+            elif r == 5:
+                r = b
+            elif r == 6:
+                r = c
+            elif r == 7:
+                die
+        else:
+            pass # literal
+
+
+        if op == 0: # adv
+            a = a>>r
+        elif op == 1: # bxl
+            b ^= r
+        elif op == 2: # bst
+            b = r%8
+        elif op == 3: # jnz
+            if a != 0:
+                ip = r - 2
+        elif op == 4: # bxc
+            b ^= c
+        elif op == 5: # out
+            out.append(r%8)
+            if check and out[-1] != prog[len(out)-1]:
+                return out
+        elif op == 6:
+            b = a>>r
+        elif op == 7:
+            c = a>>r
+
+        ip += 2
+
+    print(",".join(str(x) for x in out))
+    return out
+
+simulate(729, sample)
+simulate(46337277, input)
diff --git a/day17/sol2.c b/day17/sol2.c
new file mode 100644
index 0000000..b8a6183
--- /dev/null
+++ b/day17/sol2.c
@@ -0,0 +1,88 @@
+
+
+#include <stdio.h>
+
+int prog[] = {2,4,1,1,7,5,4,4,1,4,0,3,5,5,3,0};
+int plen = sizeof(prog) /  sizeof(int);
+
+long reverse(int i, long init) {
+	long a = init;
+	// jnz,0
+	if (i >= plen) {
+		return init;
+	}
+
+	// in,5
+	int b = prog[plen-i-1];
+
+	// adv,3,
+	a <<= 3l;
+
+	// bxl,4
+	b ^= 4;
+
+	// cdv,5
+	// bxc,4
+	long q;
+	for (q = 0; q < 8; q++) {
+		if (((q^1) ^ ((((a|q)>>(q^1)))&7)) == b) {
+			// bst 4
+			// bxl,1
+			long x = reverse(i+1, a|q);
+			if (x >= 0) {
+				return x;
+			}
+		}
+	}
+
+	//error
+	if (a == 0) {
+		return -1;
+	}
+	return -a;
+}
+
+
+int run(long a) {
+	int b = 0;
+	int c = 0;
+	int i = 0;
+
+	// 4:a 5:b 6:c
+	do {
+
+	// bst 4
+	b = a%8;
+	//
+	// bxl,1
+	b ^= 1;
+	// cdv,5
+	c = (a&65535) >> b;
+	// bxc,4
+	b ^= c;
+	// bxl,4
+	b ^= 4;
+	// adv,3,
+	a >>= 3;
+	// out,5
+	printf("%d", b%8);
+	if (i >= plen || (b%8) != prog[i]) {
+		printf("!");
+	}
+	printf(" ");
+	i++;
+
+	// jnz,0
+	} while (a != 0);
+
+	printf("\n");
+	return 0;
+}
+
+
+int main() {
+	long a = reverse(0, 0);
+	printf("%ld\n", a);
+	run(a);
+	return 0;
+}