diff --git a/ruby/day_25.rb b/ruby/day_25.rb
new file mode 100644
index 0000000..6883d28
--- /dev/null
+++ b/ruby/day_25.rb
@@ -0,0 +1,15 @@
+row = 2981
+col = 3075
+
+i = row*(row-1)/2 + 1
+i += (row..row+col-1).inject(:+) - row
+
+value = 20151125
+(i-1).times do
+  value *= 252533
+  value %= 33554393
+end
+puts value
+
+__END__
+Enter the code at row 2981, column 3075.