diff --git a/15_1.rb b/15_1.rb
new file mode 100644
index 0000000..af71bd8
--- /dev/null
+++ b/15_1.rb
@@ -0,0 +1,30 @@
+GEN_A_START = 679
+GEN_B_START = 771
+GEN_A_TEST_S = 65
+GEN_B_TEST_S = 8921
+
+GEN_A_FAC = 16807
+GEN_B_FAC = 48271
+
+MOD = 2147483647
+
+def compare a, b
+  a_bin = a.to_s(2)[-16..-1]
+  b_bin = b.to_s(2)[-16..-1]
+  a_bin == b_bin
+end
+
+matches = 0
+
+a_rem = GEN_A_START
+b_rem = GEN_B_START
+
+for i in 1..(40*10**6) do
+  if i % 1000000 == 0 then puts i end
+  a_rem = (a_rem * GEN_A_FAC) % MOD
+  b_rem = (b_rem * GEN_B_FAC) % MOD 
+  if compare a_rem,b_rem then matches += 1 end
+end
+
+puts matches
+
diff --git a/15_2.rb b/15_2.rb
new file mode 100644
index 0000000..cfc0b19
--- /dev/null
+++ b/15_2.rb
@@ -0,0 +1,40 @@
+GEN_A_START = 679
+GEN_B_START = 771
+GEN_A_TEST_S = 65
+GEN_B_TEST_S = 8921
+GEN_A_P = 4
+GEN_B_P = 8
+
+GEN_A_FAC = 16807
+GEN_B_FAC = 48271
+
+MOD = 2147483647
+
+def compare a, b
+  a_bin = a.to_s(2)[-16..-1]
+  b_bin = b.to_s(2)[-16..-1]
+  a_bin == b_bin
+end
+
+matches = 0
+
+def find_next val, fac, mul
+  while(true) do
+    val = (val * fac) % MOD
+    break if val % mul == 0
+  end
+  val
+end
+
+a_rem = GEN_A_START
+b_rem = GEN_B_START
+
+for i in 1..(5*10**6) do
+  if i % 1000000 == 0 then puts i end
+  a_rem = find_next a_rem, GEN_A_FAC, GEN_A_P
+  b_rem = find_next b_rem, GEN_B_FAC, GEN_B_P
+  if compare a_rem, b_rem then matches +=1 end
+end
+
+puts matches
+