diff --git a/main.cpp b/main.cpp
index 4d9a9a4..73074d6 100644
--- a/main.cpp
+++ b/main.cpp
@@ -15,7 +15,7 @@ struct Input {
 };
 
 Input
-input_data() {
+input_data(istream& Newcin) {
     size_t number_count;
     cerr << "Enter number count: ";
     cin >> number_count;
@@ -36,7 +36,7 @@ input_data() {
 
 int
 main() {
-    auto in = input_data();
+auto in = input_data(cin);
     auto bins = make_histogram(in.numbers, in.bin_count);
     show_histogram_svg(bins, in.stroke, in.fill);
 }