diff --git a/task_01/src/test.cpp b/task_01/src/test.cpp
index ef5a86ae..b086e16e 100644
--- a/task_01/src/test.cpp
+++ b/task_01/src/test.cpp
@@ -3,6 +3,16 @@
 
 #include "topology_sort.hpp"
 
-TEST(TopologySort, Simple) {
-  ASSERT_EQ(1, 1);  // Stack []
-}
+TEST(find_pair_with_sum, Simple) {
+  std::vector<int> test1 = {2, 3, 7, 12, 13, 28, 30, 60};
+
+  ASSERT_EQ(find_pair_with_sum(test1, 14), std::make_pair(0, 3));
+  ASSERT_EQ(find_pair_with_sum(test1, 20), std::make_pair(2, 4));
+  ASSERT_EQ(find_pair_with_sum(test1, 21), std::make_pair(-1, -1));
+  ASSERT_EQ(find_pair_with_sum(test1, 58), std::make_pair(5, 6));
+  ASSERT_EQ(find_pair_with_sum(test1, 70), std::make_pair(-1, -1));
+  ASSERT_EQ(find_pair_with_sum(test1, -12312), std::make_pair(-1, -1));
+
+  std::vector<int> test2 = {};
+  ASSERT_EQ(find_pair_with_sum(test2, 1), std::make_pair(-1, -1));
+}
\ No newline at end of file
diff --git a/task_01/src/topology_sort.cpp b/task_01/src/topology_sort.cpp
index e53f670c..6b3429e4 100644
--- a/task_01/src/topology_sort.cpp
+++ b/task_01/src/topology_sort.cpp
@@ -1 +1,22 @@
 #include "topology_sort.hpp"
+
+std::pair<int, int> find_pair_with_sum(std::vector<int> mass, int a) {
+  if (!std::is_sorted(mass.begin(), mass.end()) or mass.size() == 0) {
+    return std::pair<int, int>(-1, -1);
+  }
+  int L = 0;
+  int R = mass.size() - 1;
+
+  while (L != R) {
+    if (mass[L] + mass[R] == a) {
+      return std::pair<int, int>(L, R);
+    }
+    if (mass[L] + mass[R] < a) {
+      L += 1;
+    } else {
+      R -= 1;
+    }
+  }
+
+  return std::pair<int, int>(-1, -1);
+}
diff --git a/task_01/src/topology_sort.hpp b/task_01/src/topology_sort.hpp
index 6f70f09b..033c4f5e 100644
--- a/task_01/src/topology_sort.hpp
+++ b/task_01/src/topology_sort.hpp
@@ -1 +1,6 @@
 #pragma once
+
+#include <algorithm>
+#include <vector>
+
+std::pair<int, int> find_pair_with_sum(std::vector<int> mass, int a);
\ No newline at end of file