diff --git a/histogram.cpp b/histogram.cpp
index 4c759c6..c65e454 100644
--- a/histogram.cpp
+++ b/histogram.cpp
@@ -3,41 +3,47 @@
 #include <iostream>
 using namespace std;
 
-void
+bool
 find_minmax(const vector<double>& numbers, double& min, double& max) {
-    min = numbers[0];
-    max = numbers[0];
-    for (double x : numbers) {
-        if (x < min) {
-            min = x;
-        }
-        else if (x > max) {
-            max = x;
-        }
-    }
+	if (numbers.empty()) {
+		return false;
+	}
+
+	min = numbers[0];
+	max = numbers[0];
+	for (double x : numbers) {
+		if (x < min) {
+			min = x;
+		}
+		else if (x > max) {
+			max = x;
+		}
+	}
+
+	return true;
 }
 
 std::vector<double>
 make_histogram(const std::vector<double>& numbers, size_t bin_count) {
-    vector<double> bins(bin_count);
+	vector<double> bins(bin_count);
 
-    double min = 0, max = 0;
-    find_minmax(numbers, min, max);
+	double min = 0, max = 0;
+	find_minmax(numbers, min, max);
 
-    double bin_size = (max - min) / bin_count;
-    for (int i = 0; i < numbers.size(); i++) {
-        bool found = false;
-        for (int j = 0; (j < bin_count - 1) && !found; j++) {
-            auto lo = min + j * bin_size;
-            auto hi = min + (j + 1) * bin_size;
-            if ((lo <= numbers[i]) && (numbers[i] < hi)) {
-                bins[j]++;
-                found = true;
-            }
-        }
-        if (!found) {
-            bins[bin_count - 1]++;
-        }
-    }
-    return bins;
+	double bin_size = (max - min) / bin_count;
+	for (int i = 0; i < numbers.size(); i++) {
+		bool found = false;
+		for (int j = 0; (j < bin_count - 1) && !found; j++) {
+			auto lo = min + j * bin_size;
+			auto hi = min + (j + 1) * bin_size;
+			if ((lo <= numbers[i]) && (numbers[i] < hi)) {
+				bins[j]++;
+				found = true;
+			}
+		}
+		if (!found) {
+			bins[bin_count - 1]++;
+		}
+	}
+	return bins;
 }
diff --git a/histogram_internal.h b/histogram_internal.h
index a6ef22d..bc6165c 100644
--- a/histogram_internal.h
+++ b/histogram_internal.h
@@ -1,4 +1,4 @@
 #pragma once
 #include <vector>
-void
+bool
 find_minmax(const std::vector<double>& numbers, double& min, double& max);
\ No newline at end of file
diff --git a/main.cpp b/main.cpp
index f233c47..8568006 100644
--- a/main.cpp
+++ b/main.cpp
@@ -21,42 +21,42 @@ input_data() {
     cerr << "Enter number count: ";
     cin >> number_count;
 
-    Input in;
-    in.numbers.resize(number_count);
+    Input in1;
+    in1.numbers.resize(number_count);
     cerr << "Enter numbers: ";
     for (size_t i = 0; i < number_count; i++) {
-        cin >> in.numbers[i];
+        cin >> in1.numbers[i];
     }
 
     cerr << "Enter bin count: ";
-    cin >> in.bin_count;
+    cin >> in1.bin_count;
 
  
     cerr << "Enter stroke colour without spaces or in code format:";
     cin.ignore();
-    getline(cin, in.stroke);
+    getline(cin, in1.stroke);
 
-    for (i = 0; i < in.stroke.length(); i++) {
-        if (isspace(in.stroke[i])) {
+    for (i = 0; i < in1.stroke.length(); i++) {
+        if (isspace(in1.stroke[i])) {
             cerr << "invalid input";
             exit(0);
         }
     }
-    if (in.stroke[0] == check2[0]) {
-        if (in.stroke.length() != 7) {
+    if (in1.stroke[0] == check2[0]) {
+        if (in1.stroke.length() != 7) {
             cerr << "invalid input";
             exit(0);
         }
     }
-    return in;
+    return in1;
 }
 
 int main()
 {
     const size_t SCREEN_WIDTH = 80;
     const size_t MAX_ASTERISK = SCREEN_WIDTH - 3 - 1;
-    auto in = input_data();
-    auto bins = make_histogram(in.numbers, in.bin_count);
-    show_histogram_svg(bins, in.stroke);
+    auto in1 = input_data();
+    auto bins = make_histogram(in1.numbers, in1.bin_count);
+    show_histogram_svg(bins, in1.stroke);
     return 0;
 }
diff --git a/unittest.cpp b/unittest.cpp
index f91aa73..44c8a0a 100644
--- a/unittest.cpp
+++ b/unittest.cpp
@@ -13,9 +13,7 @@ TEST_CASE("distinct positive numbers") {
 TEST_CASE("empty vector") {
 	double min = 0;
 	double max = 0;
-	find_minmax({NULL}, min, max);
-	CHECK(min == 0);
-	CHECK(max == 0);
+	CHECK(!find_minmax({}, min, max));
 }
 TEST_CASE("one element") {
 	double min = 0;