diff --git a/src/day3.cpp b/src/day3.cpp
index 05bb45b..59c9b65 100644
--- a/src/day3.cpp
+++ b/src/day3.cpp
@@ -26,14 +26,14 @@ char get_max_char(std::string_view s) {
 }
 
 int64_t solve(const std::string_view line, size_t cnt_to_activate) {
-  const auto search{line.substr(0, line.size() - cnt_to_activate + 1)};
+  const std::string_view search{line.substr(0, line.size() - cnt_to_activate + 1)};
   const char max_char{get_max_char(search)}, null_terminator{'\0'};
-  const auto max_char_idx{search.find(&max_char, 0)};
+  const size_t max_char_idx{search.find(&max_char, 0)};
   const int64_t max_char_as_int = max_char - '0';
   if (cnt_to_activate == 1) {
     return max_char_as_int;
   }
-  const auto recur{solve(line.substr(max_char_idx + 1), cnt_to_activate - 1)};
+  const int64_t recur{solve(line.substr(max_char_idx + 1), cnt_to_activate - 1)};
   // slightly hacky... integral concat better?
   return std::stoll(std::string(&max_char) + std::to_string(recur));
 }