diff --git a/source/day9.d b/source/day9.d
index f39de5f..8af8ed0 100644
--- a/source/day9.d
+++ b/source/day9.d
@@ -11,21 +11,67 @@ Variant run(int part, File input, bool bigboy, string[] args) {
 	import std.conv;
 	auto numbers = input.byLineCopy.array.map!(to!uint);
 	return Variant(parts!uint(part,
-				() => part1(numbers)));
+				() => part1(numbers),
+				() => part2(numbers)));
 }
 
-T part1(Range, T = ElementType!Range)(Range range, int preambleSize = 25) 
-	if (isForwardRange!Range && isNumeric!T) {
-	foreach(window; range.slide!(No.withPartial)(preambleSize + 1)) {
+ptrdiff_t indexOfWeakness(Range)(Range range, int preambleSize = 25) 
+	if (isForwardRange!Range)
+	in (range.length > preambleSize)
+	out (r; r >= preambleSize || r == -1)
+do {
+	foreach(i, window; range.slide!(No.withPartial)(preambleSize + 1).enumerate) {
 		if(!window[0..preambleSize].any!(e => window.canFind!(x => e + x == window[preambleSize]))) {
-			return window[preambleSize];
+			return preambleSize + i;
 		}
 	}
 	return -1;
 }
 
+T part1(Range, T = ElementType!Range)(Range range, int preambleSize = 25)
+	if (isForwardRange!Range)
+	in (range.length > preambleSize) {
+	
+	auto index = indexOfWeakness(range, preambleSize);
+	assert(index >= 0);
+	return range[index];
+}
+
 unittest {
 	int[] numbers = [35, 20, 15, 25, 47, 40, 62, 55, 65, 95, 102, 117, 150, 182, 127, 219, 299, 
 		277, 309, 576];
 	assert(part1(numbers, 5) == 127);
 }
+
+T part2(Range, T = ElementType!Range)(Range range, int preambleSize = 25)
+	if (isForwardRange!Range)
+	in (range.length > preambleSize)
+do {
+	
+	T num = part1(range, preambleSize);
+
+	for (size_t offset = 0; offset <= range.length; offset++) {
+		T min = T.max;
+		T max = T.min;
+
+		size_t offset_offset = 0;
+		T sum = 0;
+		for(; sum < num && offset + offset_offset < range.length; sum += range[offset + offset_offset++]) {
+			T curNumber = range[offset + offset_offset];
+			if (curNumber < min) min = curNumber;
+			if (curNumber > max) max = curNumber;
+		}
+
+		if (sum == num) {
+			return min + max;
+		}
+	}
+
+	return -1;
+}
+
+unittest {
+	int[] numbers = [35, 20, 15, 25, 47, 40, 62, 55, 65, 95, 102, 117, 150, 182, 127, 219, 299, 
+		277, 309, 576];
+	assert(part2(numbers, 5) == 62);
+}