diff --git a/src/main/kotlin/Day4.kt b/src/main/kotlin/Day4.kt
index 837de32..65f0731 100644
--- a/src/main/kotlin/Day4.kt
+++ b/src/main/kotlin/Day4.kt
@@ -1,6 +1,4 @@
 import java.io.File
-import java.lang.Integer.max
-import java.lang.Integer.min
 
 fun main() {
     println("Hello day4!")
@@ -19,20 +17,20 @@ fun solveDay4() {
 
 fun conpleteOverlap(line: String): Boolean {
     val number = "(\\d+)-(\\d+),(\\d+)-(\\d+)".toRegex()
-    val l = number.find(line)!!.groupValues.stream().skip(1).map { Integer.valueOf(it) }.toList()
+    val l = number.find(line)!!.groupValues.drop(1).map { Integer.valueOf(it) }
 
-    val min = min(l[0], l[2])
-    val max = max(l[1], l[3])
+    val min = minOf(l[0], l[2])
+    val max = maxOf(l[1], l[3])
 
     return (min == l[0] && max == l[1]) || (min == l[2] && max == l[3])
 }
 
 fun partialOverlap(line: String): Boolean {
     val number = "(\\d+)-(\\d+),(\\d+)-(\\d+)".toRegex()
-    val l = number.find(line)!!.groupValues.stream().skip(1).map { Integer.valueOf(it) }.toList()
+    val l = number.find(line)!!.groupValues.drop(1).map { Integer.valueOf(it) }.toList()
 
-    val max = max(l[0], l[2])
-    val min = min(l[1], l[3])
+    val max = maxOf(l[0], l[2])
+    val min = minOf(l[1], l[3])
 
     return min >= max
 }
\ No newline at end of file