cin меняем на in

main.cpp

@@ -5,21 +5,21 @@ struct Input {
     vector<double> vec;
     size_t korz{};
 };
-Input input_data() {
-    Input in;
+Input input_data(istream& in) {
+    Input lin;
     size_t n, korz;
 
     cerr << "Number of elem ";
-    cin >> n;
-    in.vec.resize(n);
+    in >> n;
+    lin.vec.resize(n);
     for (size_t i = 0; i < n; i++)
-        cin >> in.vec[i];
+        in >> lin.vec[i];
     cerr << "Enter bin count: ";
-    cin >> in.korz;
-    return in;
+    in >> lin.korz;
+    return lin;
 }
 int main() {
-    auto in = input_data();
+    auto in = input_data(cin);
     auto bins = make_histogram(in.korz, in.vec);
     show_histogram_svg(bins);
 }