diff --git a/2016/day25/main.go b/2016/day25/main.go
new file mode 100644
index 0000000..165953a
--- /dev/null
+++ b/2016/day25/main.go
@@ -0,0 +1,57 @@
+package main
+
+import (
+	"flag"
+	"fmt"
+	"math"
+	"regexp"
+
+	"github.com/alexchao26/advent-of-code-go/cast"
+	"github.com/alexchao26/advent-of-code-go/util"
+)
+
+func main() {
+	var part int
+	flag.IntVar(&part, "part", 1, "part 1 or 2")
+	flag.Parse()
+	fmt.Println("Running part", part)
+
+	ans := part1(util.ReadFile("./input.txt"))
+	fmt.Println("Output:", ans)
+}
+
+func part1(input string) int {
+	for i := 0; i < math.MaxInt32; i++ {
+		if assemblyComputer(input, i) {
+			return i
+		}
+	}
+	return -1
+}
+
+func assemblyComputer(input string, registerAInitialValue int) bool {
+	pattern := regexp.MustCompile("^(01){1,}$")
+	var outputs string
+
+	var a, b, d int
+
+	a = registerAInitialValue
+	d = a + 2532
+	for {
+		a = d
+		for a != 0 {
+			b = a % 2
+			a /= 2
+			outputs += cast.ToString(b)
+			if len(outputs)%2 == 0 {
+				if !pattern.MatchString(outputs) {
+					return false
+				} else if len(outputs) > 100 {
+					return true
+				}
+			}
+		}
+	}
+
+	panic("should return from loop")
+}
diff --git a/2016/day25/main_test.go b/2016/day25/main_test.go
new file mode 100644
index 0000000..22a4487
--- /dev/null
+++ b/2016/day25/main_test.go
@@ -0,0 +1,39 @@
+package main
+
+import (
+	"testing"
+)
+
+func Test_part1(t *testing.T) {
+	tests := []struct {
+		name  string
+		input string
+		want  int
+	}{
+		// {"actual", util.ReadFile("input.txt"), ACTUAL_ANSWER},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := part1(tt.input); got != tt.want {
+				t.Errorf("part1() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}
+
+func Test_part2(t *testing.T) {
+	tests := []struct {
+		name  string
+		input string
+		want  int
+	}{
+		// {"actual", util.ReadFile("input.txt"), ACTUAL_ANSWER},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := part2(tt.input); got != tt.want {
+				t.Errorf("part2() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}