diff --git a/dp/dp_test.go b/dp/dp_test.go
new file mode 100644
index 0000000..fbd1a17
--- /dev/null
+++ b/dp/dp_test.go
@@ -0,0 +1,53 @@
+package dp
+
+import (
+	"fmt"
+	"testing"
+)
+
+func countThePath(grid [][]int) int {
+	if len(grid) == 0 || len(grid[0]) == 0 {
+		return 0
+	}
+	opt := make([][]int, len(grid))
+	for i := 0; i < len(grid); i++ {
+		opt[i] = make([]int, len(grid[i]))
+	}
+	for i := len(grid) - 1; i >= 0; i-- {
+		for j := len(grid[i]) - 1; j >= 0; j-- {
+			if i+1 >= len(grid) {
+				opt[i][j] = 1
+				continue
+			}
+			if j+1 >= len(grid[i]) {
+				opt[i][j] = 1
+				continue
+			}
+			if grid[i+1][j] == 0 {
+				opt[i][j] += opt[i+1][j]
+			}
+			if grid[i][j+1] == 0 {
+				opt[i][j] += opt[i][j+1]
+			}
+		}
+	}
+	fmt.Scanln()
+	for _, r := range opt {
+		fmt.Println(r)
+	}
+	return opt[0][0]
+}
+
+func Test_countThePath(t *testing.T) {
+	grid := [][]int{
+		{0, 0, 0, 0, 0, 0, 0, 0},
+		{0, 0, 1, 0, 0, 0, 1, 0},
+		{0, 0, 0, 0, 1, 0, 0, 0},
+		{1, 0, 1, 0, 0, 1, 0, 0},
+		{0, 0, 1, 0, 0, 0, 0, 0},
+		{0, 0, 0, 1, 1, 0, 1, 0},
+		{0, 1, 0, 0, 0, 1, 0, 0},
+		{0, 0, 0, 0, 0, 0, 0, 0},
+	}
+	fmt.Println(countThePath(grid))
+}
diff --git a/go.mod b/go.mod
index 6224274..52e40fe 100644
--- a/go.mod
+++ b/go.mod
@@ -1,3 +1,3 @@
-module leetcode
+module github.com/Aavon/leetcode
 
 go 1.12
diff --git a/s4/solution_test.go b/s4/solution_test.go
new file mode 100644
index 0000000..2202a2f
--- /dev/null
+++ b/s4/solution_test.go
@@ -0,0 +1,5 @@
+package s4
+
+func solution() {
+
+}