diff --git a/first-bad-version/sol.go b/first-bad-version/sol.go
new file mode 100644
index 0000000..de257e6
--- /dev/null
+++ b/first-bad-version/sol.go
@@ -0,0 +1,19 @@
+package main
+
+func isBadVersion(version int) bool
+
+// Time: O(log(n))
+// Space: O(1)
+func firstBadVersion(n int) int {
+	move := 0
+	for n > 1 {
+		p := n / 2
+		if isBadVersion(move + p) {
+			n = p
+		} else {
+			n = n - p
+			move += p
+		}
+	}
+	return move + n
+}