diff --git a/common/in.go b/common/in.go
new file mode 100644
index 0000000..1ff46a7
--- /dev/null
+++ b/common/in.go
@@ -0,0 +1,13 @@
+package common
+
+// In picks x if y < x, picks z if y > z, or if none of the previous
+// conditions is satisfies, it simply picks y.
+func In(x, y, z int) {
+	switch {
+	case y < x:
+		return x
+	case y > z:
+		return z
+	}
+	return y
+}