diff --git a/2025/three/three.go b/2025/three/three.go
new file mode 100644
index 0000000..d203385
--- /dev/null
+++ b/2025/three/three.go
@@ -0,0 +1,87 @@
+package main
+
+import (
+	"bufio"
+	"fmt"
+	"log"
+	"os"
+	"strconv"
+)
+
+func parseBank(text string) []int {
+	bank := make([]int, 0, len(text))
+	for _, char := range text {
+		battery, err := strconv.Atoi(string(char))
+		if err != nil {
+			panic(err)
+		}
+		bank = append(bank, battery)
+	}
+
+	return bank
+}
+
+func main() {
+
+	file, err := os.Open("three.txt")
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer file.Close()
+
+	scanner := bufio.NewScanner(file)
+	ch := make(chan int)
+	n_banks := 0
+	jolts := 0
+
+	for scanner.Scan() {
+		n_banks++
+		text := scanner.Text()
+
+		bank := parseBank(text)
+
+		go joltage(bank, ch)
+	}
+
+	for i := 0; i < n_banks; i++ {
+		jolts += <-ch
+	}
+
+	fmt.Println(jolts)
+}
+
+func joltage(bank []int, ch chan int) {
+	ch <- _joltage(bank)
+}
+
+func _joltage(bank []int) int {
+	out := 0
+
+	startIndex := 0
+
+	for endIndex := len(bank) - 11; endIndex <= len(bank); endIndex++ {
+
+		out *= 10
+		highest, index := highestEarly(bank, startIndex, endIndex)
+		out += highest
+		startIndex = index + 1
+
+	}
+
+	return out
+}
+
+func highestEarly(bank []int, start int, end int) (int, int) {
+	highest := 0
+	index := 0
+
+	for i := start; i < end; i++ {
+		val := bank[i]
+		if val > highest {
+			highest = val
+			index = i
+		}
+	}
+
+	return highest, index
+}
diff --git a/2025/three/three_test.go b/2025/three/three_test.go
new file mode 100644
index 0000000..8cbfd4f
--- /dev/null
+++ b/2025/three/three_test.go
@@ -0,0 +1,56 @@
+package main
+
+import "testing"
+
+type highestTest struct {
+	bank                    string
+	start                   int
+	end                     int
+	expected, expectedIndex int
+}
+
+var highestTests = []highestTest{
+	{"999", 0, 3, 9, 0},
+	{"919", 0, 3, 9, 0},
+	{"919", 1, 3, 9, 2},
+	{"818181911112111", 0, 4, 8, 0},
+	{"818181911112111", 1, 5, 8, 2},
+	{"818181911112111", 3, 6, 8, 4},
+	{"818181911112111", 5, 7, 9, 6},
+}
+
+func TestHhigest(t *testing.T) {
+	for _, test := range highestTests {
+		highest, index := highestEarly(parseBank(test.bank), test.start, test.end)
+
+		if highest != test.expected {
+			t.Errorf("Expected %d got %d for bank %v", test.expected, highest, test.bank)
+		}
+
+		if index != test.expectedIndex {
+			t.Errorf("Expected %d got %d for bank %v", test.expectedIndex, index, test.bank)
+		}
+	}
+}
+
+type joltageTest struct {
+	bank     string
+	expected int
+}
+
+var joltageTests = []joltageTest{
+	{"987654321111111", 987654321111},
+	{"811111111111119", 811111111119},
+	{"234234234234278", 434234234278},
+	{"818181911112111", 888911112111},
+}
+
+func TestJoltage(t *testing.T) {
+	for _, test := range joltageTests {
+		out := _joltage(parseBank(test.bank))
+
+		if out != test.expected {
+			t.Errorf("Expected %d got %d for bank %v", test.expected, out, test.bank)
+		}
+	}
+}