diff --git a/20201230/main.go b/20201230/main.go
new file mode 100644
index 0000000..0ccb252
--- /dev/null
+++ b/20201230/main.go
@@ -0,0 +1,36 @@
+package main
+
+func main() {
+
+}
+
+func process(nums []int) []int {
+	var ret []int
+	c := 0
+	for {
+		if len(ret) == len(nums) {
+			break
+		}
+		n := findNextLarge(c, nums)
+		ret = append(ret, n)
+		c++
+	}
+	return ret
+}
+
+func findNextLarge(index int, nums []int) int {
+	if index > len(nums)-1 {
+		return -1
+	}
+	src := append(nums[index+1:], nums[:index+1]...)
+	for i, c := range src {
+		if c > nums[index] {
+			x := index + i + 1
+			if x > len(nums) {
+				x -= len(nums)
+			}
+			return c
+		}
+	}
+	return -1
+}
diff --git a/20201230/main_test.go b/20201230/main_test.go
new file mode 100644
index 0000000..6d7d8df
--- /dev/null
+++ b/20201230/main_test.go
@@ -0,0 +1,84 @@
+package main
+
+import (
+	"reflect"
+	"testing"
+)
+
+func Test_process(t *testing.T) {
+	type args struct {
+		nums []int
+	}
+	tests := []struct {
+		name string
+		args args
+		want []int
+	}{
+		{
+			"test1",
+			args{
+				nums: []int{1, 2, 1},
+			},
+			[]int{2, -1, 2},
+		},
+		{
+			"test2",
+			args{
+				nums: []int{1},
+			},
+			[]int{-1},
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := process(tt.args.nums); !reflect.DeepEqual(got, tt.want) {
+				t.Errorf("process() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}
+
+func Test_findNextLarge(t *testing.T) {
+	type args struct {
+		index int
+		nums  []int
+	}
+	tests := []struct {
+		name string
+		args args
+		want int
+	}{
+		{
+			"test1",
+			args{
+				1,
+				[]int{1, 2, 3},
+			},
+			3,
+		},
+		{
+			"test2",
+			args{
+				0,
+				[]int{1, 2, 3},
+			},
+			2,
+		},
+		{
+			"test3",
+			args{
+				2,
+				[]int{1, 2, 3},
+			},
+			-1,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got := findNextLarge(tt.args.index, tt.args.nums)
+			if got != tt.want {
+				t.Errorf("findNextLarge() got = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}