diff --git a/algorithm.h b/algorithm.h
index 0037651..29e0ae7 100644
--- a/algorithm.h
+++ b/algorithm.h
@@ -46,9 +46,9 @@ namespace firefly::std {
     }
 
     template <typename InputIt, typename UnaryPredicate>
-    std::size_t count_if(InputIt first, const InputIt last, 
+    size_t count_if(InputIt first, const InputIt last, 
         UnaryPredicate func) {
-        std::size_t count = 0;
+        size_t count = 0;
 
         for (; first != last; first++) {
             if (func(*first))
@@ -58,9 +58,9 @@ namespace firefly::std {
         return count;
     }
 
-    template <typename InputIt, typename T> std::size_t count(InputIt first, const InputIt last,
+    template <typename InputIt, typename T> size_t count(InputIt first, const InputIt last,
         const T& lval) {
-        std::size_t count = 0;
+        size_t count = 0;
         
         for (; first != last; first++) {
             if (*first == lval)
@@ -70,6 +70,28 @@ namespace firefly::std {
         return count;
     }
 
+    template <typename InputIt> size_t
+    accumulate(InputIt begin, InputIt end) {
+        size_t sum = 0;
+
+        while (begin != end) {
+            sum += *begin;
+        }
+
+        return sum;
+    }
+
+    template <typename InputIt, typename Op> size_t
+    accumulate(InputIt begin, InputIt end, Op op) {
+        size_t sum = 0;
+
+        while (begin != end) {
+            sum = op(sum, *begin);
+        }
+
+        return sum;
+    }
+
     /*
     template <class RandomIt>
     void sort(RandomIt first, RandomIt last) {