diff --git a/advent_of_code/2015/6/src/main.rs b/advent_of_code/2015/6/src/main.rs
index 1c88622..02cf79b 100644
--- a/advent_of_code/2015/6/src/main.rs
+++ b/advent_of_code/2015/6/src/main.rs
@@ -26,18 +26,18 @@ struct Instruction<T> {
     second_coord: Coord<T>,
 }
 
-fn parse_input(input: &str) -> IResult<&str, Vec<Instruction<u64>>> {
+fn parse_input(input: &str) -> IResult<&str, Vec<Instruction<i64>>> {
     let (input, result) = separated_list1(
         multispace1,
         tuple((
             alt((tag("toggle "), tag("turn on "), tag("turn off "))),
-            complete::u64,
+            complete::i64,
             tag(","),
-            complete::u64,
+            complete::i64,
             tag(" through "),
-            complete::u64,
+            complete::i64,
             tag(","),
-            complete::u64,
+            complete::i64,
         ))
         .map(|(switch, x_1, _, y_1, _, x_2, _, y_2)| Instruction {
             switch: match switch {
@@ -54,7 +54,7 @@ fn parse_input(input: &str) -> IResult<&str, Vec<Instruction<u64>>> {
     Ok((input, result))
 }
 
-fn solve_first(input: &[Instruction<u64>]) -> usize {
+fn solve_first(input: &[Instruction<i64>]) -> usize {
     let mut lights = vec![false; GRID_MAX * GRID_MAX];
 
     for instruction in input.iter() {
@@ -75,6 +75,25 @@ fn solve_first(input: &[Instruction<u64>]) -> usize {
     })
 }
 
+fn solve_second(input: &[Instruction<i64>]) -> i64 {
+    let mut lights = vec![0; GRID_MAX * GRID_MAX];
+
+    for instruction in input.iter() {
+        for y in instruction.first_coord.y..=instruction.second_coord.y {
+            for x in instruction.first_coord.x..=instruction.second_coord.x {
+                let pos = x as usize + y as usize * GRID_MAX;
+                lights[pos] = match instruction.switch {
+                    LightSwitch::Toggle => lights[pos] + 2,
+                    LightSwitch::Off => std::cmp::max(0, lights[pos] - 1),
+                    LightSwitch::On => lights[pos] + 1,
+                }
+            }
+        }
+    }
+
+    lights.into_iter().sum()
+}
+
 fn main() {
     println!("Hello, this is Patrick!");
 
@@ -84,4 +103,8 @@ fn main() {
     let first_result = solve_first(&light_instructions[..]);
 
     println!("The number of lit light is {}", first_result);
+
+    let second_result = solve_second(&light_instructions[..]);
+
+    println!("The total brightness is {}", second_result);
 }