diff --git a/.gitea/workflows/build_and_run.yml b/.gitea/workflows/build_and_run.yml
index b050cac..c898a80 100644
--- a/.gitea/workflows/build_and_run.yml
+++ b/.gitea/workflows/build_and_run.yml
@@ -11,7 +11,7 @@ jobs:
     name: Challenge for day
     strategy:
       matrix:
-        day_number: [1, 2, 3, 4, 5, 6]
+        day_number: [1, 2, 3, 4, 5, 6, 7]
     runs-on: rust-bookworm
     steps:
       - name: Check out repository code
diff --git a/day7/Cargo.toml b/day7/Cargo.toml
new file mode 100644
index 0000000..c71629c
--- /dev/null
+++ b/day7/Cargo.toml
@@ -0,0 +1,6 @@
+[package]
+name = "day7"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]
diff --git a/day7/src/main.rs b/day7/src/main.rs
new file mode 100644
index 0000000..4669d97
--- /dev/null
+++ b/day7/src/main.rs
@@ -0,0 +1,100 @@
+use std::{env, fs};
+
+fn read_input(path: &str) -> String {
+    fs::read_to_string(path).expect("Cannot read file.")
+}
+
+fn add(a: u64, b: u64) -> u64 {
+    a + b
+}
+
+fn mul(a: u64, b: u64) -> u64 {
+    a * b
+}
+
+fn concat(a: u64, b: u64) -> u64 {
+    format!("{a}{b}").parse().unwrap()
+}
+
+fn parse_input(input: &str) -> Vec<(u64, Vec<u64>)> {
+    input
+        .lines()
+        .filter(|line| !line.is_empty())
+        .map(|line| {
+            let split_line = line.split_once(": ").unwrap();
+            (
+                split_line.0.parse().unwrap(),
+                split_line
+                    .1
+                    .split_whitespace()
+                    .map(|s| s.parse().unwrap())
+                    .rev()
+                    .collect(),
+            )
+        })
+        .collect()
+}
+
+fn is_valid(data: &mut Vec<u64>, acc: u64, target: u64, operators: &Vec<&fn(u64, u64) -> u64>) -> bool {
+    if data.is_empty() {
+        return target == acc;
+    }
+
+    if acc > target {
+        return false;
+    }
+
+    let old = data.pop().unwrap();
+    for operator in operators {
+        if is_valid(data, operator(acc, old), target, operators) {
+            return true;
+        }
+    }
+    data.push(old);
+    false
+}
+
+fn sum_valid(calibration_data: &Vec<(u64, Vec<u64>)>, operators: &Vec<&fn(u64, u64) -> u64>) -> u64 {
+    let mut sum_valid = 0;
+    let calibration_data = calibration_data.clone();
+
+    for calibration in calibration_data {
+        let mut x = calibration.1;
+        let acc = x.pop().unwrap();
+        if is_valid(&mut x, acc, calibration.0, operators) {
+            sum_valid += calibration.0;
+        }
+    }
+
+    sum_valid
+}
+
+fn part_1(input: &Vec<(u64, Vec<u64>)>) -> u64 {
+    let valid_operators = vec![
+        &(add as fn(u64, u64) -> u64),
+        &(mul as fn(u64, u64) -> u64)
+    ];
+
+    sum_valid(input, &valid_operators)
+}
+
+fn part_2(input: &Vec<(u64, Vec<u64>)>) -> u64 {
+    let valid_operators = vec![
+        &(add as fn(u64, u64) -> u64),
+        &(mul as fn(u64, u64) -> u64),
+        &(concat as fn(u64, u64) -> u64)
+    ];
+
+    sum_valid(input, &valid_operators)
+}
+
+fn main() {
+    let args: Vec<String> = env::args().collect();
+    for arg in args.iter().skip(1) {
+        let input = read_input(&arg);
+        let calibration_data = parse_input(&input);
+        println!("[{}]", &arg);
+        println!("\t[Part 1] => Answer is '{}'.", part_1(&calibration_data));
+        println!("\t[Part 2] => Answer is '{}'.", part_2(&calibration_data));
+    }
+}