diff --git a/day_07/src/equation.rs b/day_07/src/equation.rs
index 5acf723..2549c3f 100644
--- a/day_07/src/equation.rs
+++ b/day_07/src/equation.rs
@@ -48,10 +48,6 @@ impl Equation {
         self.answer
     }
 
-    pub fn components(&self) -> &Vec<i64> {
-        &self.components
-    }
-
     fn compute_answer(&self, operators: &[Op]) -> i64 {
         let mut accumulator = self.components[0];
 
@@ -59,6 +55,11 @@ impl Equation {
             match op {
                 Op::Multiply => accumulator *= self.components[i + 1],
                 Op::Add => accumulator += self.components[i + 1],
+                Op::CONCAT => {
+                    let accumulator_string = format!("{}", accumulator);
+                    let component_string = format!("{}", self.components[i + 1]);
+                    accumulator = (accumulator_string + &component_string).parse().unwrap();
+                }
             }
         }
 
@@ -78,4 +79,18 @@ impl Equation {
         }
         false
     }
+
+    pub fn solvable_multiply_add_concat(&self) -> bool {
+        let op_combinations = create_permutations(
+            HashSet::from([Op::Add, Op::Multiply, Op::CONCAT]),
+            self.components.len() - 1,
+        );
+
+        for combination in op_combinations {
+            if self.answer == self.compute_answer(&combination) {
+                return true;
+            }
+        }
+        false
+    }
 }
diff --git a/day_07/src/equation/operator_set.rs b/day_07/src/equation/operator_set.rs
index f1ce173..f9a5a1c 100644
--- a/day_07/src/equation/operator_set.rs
+++ b/day_07/src/equation/operator_set.rs
@@ -1,13 +1,15 @@
-use std::collections::HashMap;
 use std::collections::HashSet;
-use std::sync::{LazyLock, Mutex};
 
 #[derive(Debug, Clone, Copy, Hash, PartialEq, Eq)]
 pub enum Op {
     Multiply,
     Add,
+    CONCAT,
 }
 
+// use std::collections::HashMap;
+// use std::sync::{LazyLock, Mutex};
+
 // type OperatorCache = HashMap<usize, HashSet<Vec<Op>>>;
 
 // static OPERATOR_SET_CACHE: LazyLock<Mutex<OperatorCache>> =
diff --git a/day_07/src/main.rs b/day_07/src/main.rs
index 0d642ac..df6176b 100644
--- a/day_07/src/main.rs
+++ b/day_07/src/main.rs
@@ -33,19 +33,34 @@ fn main() -> Result<(), Box<dyn Error>> {
         equations.push(Equation::new(&line)?)
     }
 
-    let mut value_sum = 0;
+    let mut result_add_multiply = 0;
+    let mut result_add_multiply_concat = 0;
 
     println!("Is solvable?");
     println!("------------");
     for equation in equations {
-        let solvable = equation.solvable_multiply_add();
-        println!("{:?} => {}", equation, solvable);
-        if solvable {
-            value_sum += equation.answer();
+        let solvable_add_multiply = equation.solvable_multiply_add();
+        let solvable_add_multiply_concat = equation.solvable_multiply_add_concat();
+        println!(
+            "{:?} => {} | {}",
+            equation, solvable_add_multiply, solvable_add_multiply_concat
+        );
+        if solvable_add_multiply {
+            result_add_multiply += equation.answer();
+        }
+        if solvable_add_multiply_concat {
+            result_add_multiply_concat += equation.answer();
         }
     }
 
-    println!("\n Total Calibration Result: {}", value_sum);
+    println!(
+        "\n Total Calibration Result (ADD|MULTIPLY): {}",
+        result_add_multiply
+    );
+    println!(
+        "\n Total Calibration Result (ADD|MULTIPLY|CONCAT): {}",
+        result_add_multiply_concat
+    );
 
     Ok(())
 }