diff --git a/20210114/main.go b/20210114/main.go
new file mode 100644
index 0000000..88b395f
--- /dev/null
+++ b/20210114/main.go
@@ -0,0 +1,37 @@
+package main
+
+import "fmt"
+
+func main() {
+
+}
+
+func readBinaryWatch(num int) []string {
+	var ret []string
+	for h := 0; h <= 12; h++ {
+		hCount := 0
+		s := fmt.Sprintf("%#b", h)
+		for _, c := range s {
+			if c == '1' {
+				hCount++
+			}
+		}
+		for m := 0; m <= 60; m++ {
+			mCount := 0
+			s := fmt.Sprintf("%#b", m)
+			for _, c := range s {
+				if c == '1' {
+					mCount++
+				}
+			}
+			if hCount+mCount == num {
+				if m > 10 {
+					ret = append(ret, fmt.Sprintf("%d:%d", h, m))
+				} else {
+					ret = append(ret, fmt.Sprintf("%d:0%d", h, m))
+				}
+			}
+		}
+	}
+	return ret
+}
diff --git a/20210114/main_test.go b/20210114/main_test.go
new file mode 100644
index 0000000..5f0e5be
--- /dev/null
+++ b/20210114/main_test.go
@@ -0,0 +1,36 @@
+package main
+
+import (
+	"reflect"
+	"sort"
+	"testing"
+)
+
+func Test_readBinaryWatch(t *testing.T) {
+	type args struct {
+		num int
+	}
+	tests := []struct {
+		name string
+		args args
+		want []string
+	}{
+		{
+			"test1",
+			args{
+				1,
+			},
+			[]string{"1:00", "2:00", "4:00", "8:00", "0:01", "0:02", "0:04", "0:08", "0:16", "0:32"},
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got := readBinaryWatch(tt.args.num)
+			sort.Strings(got)
+			sort.Strings(tt.want)
+			if !reflect.DeepEqual(got, tt.want) {
+				t.Errorf("readBinaryWatch() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}