diff --git a/src/prob8.rs b/src/prob8.rs
index 3b68829..3c423f2 100644
--- a/src/prob8.rs
+++ b/src/prob8.rs
@@ -1,5 +1,5 @@
-use petgraph::prelude::*;
 use petgraph::matrix_graph::MatrixGraph;
+use petgraph::prelude::*;
 
 pub fn solve_part1(content: &str) -> color_eyre::Result<u32> {
     let (n_line, numbers) = {
@@ -26,6 +26,24 @@ pub fn solve_part1(content: &str) -> color_eyre::Result<u32> {
         for i in 0..m_element {
             let idx = j * m_element + i;
             idx_slice[idx] = graph.add_node(num_slice[idx]);
+            if (i as i64 - 1) >= 0 {
+                let previous_same_row = idx - 1;
+                graph.add_edge(idx_slice[idx], idx_slice[previous_same_row], num_slice[idx]);
+                graph.add_edge(
+                    idx_slice[previous_same_row],
+                    idx_slice[idx],
+                    num_slice[previous_same_row],
+                );
+            }
+            if (j as i64 - 1) >= 0 {
+                let previous_same_col = idx - m_element;
+                graph.add_edge(idx_slice[idx], idx_slice[previous_same_col], num_slice[idx]);
+                graph.add_edge(
+                    idx_slice[previous_same_col],
+                    idx_slice[idx],
+                    num_slice[previous_same_col],
+                );
+            }
         }
     }