diff --git a/hackpack/structures/bindex/bindex.cpp b/hackpack/structures/bindex/bindex.cpp
new file mode 100644
index 0000000..c1067ad
--- /dev/null
+++ b/hackpack/structures/bindex/bindex.cpp
@@ -0,0 +1,32 @@
+#define array_size 101
+int array[array_size];
+// Note that indices start at 1; So this array holds 100 elements
+
+// Get sum from elements 1 to k
+int get_prefix_sum(int k) {
+   int sum=0;
+   for(; k; k-=(k&-k))
+      sum += array[k-1];
+   return sum;
+}
+
+// Add n to element k
+void add_to_element(int k, int n) {
+   for(; k<=array_size; k+=(k&-k))
+      array[k-1] += n;
+}
+
+// Sum from element a to b
+int range_sum(int a, int b) {
+   return get_prefix_sum(b) - get_prefix_sum(a-1);
+}
+
+// Get element k
+int get_element(int k) {
+   return range_sum(k,k);
+}
+
+// Set element k to value n
+void set_element(int k, int n) {
+   add_to_element(k, n - get_element(k));
+}
diff --git a/hackpack/structures/bindex/bindex.tex b/hackpack/structures/bindex/bindex.tex
new file mode 100644
index 0000000..e69de29