diff --git a/src/day7.cpp b/src/day7.cpp
index 8c5cb07..3f8a6fe 100644
--- a/src/day7.cpp
+++ b/src/day7.cpp
@@ -11,8 +11,8 @@
 using Grid = std::vector<std::string>;
 using Location = std::tuple<size_t, size_t>;
 
-int64_t part_1(const Grid &grid);
-int64_t part_2(const Grid &grid);
+uint64_t part_1(const Grid &grid);
+uint64_t part_2(const Grid &grid);
 
 int main() {
   Grid grid;
@@ -38,15 +38,15 @@ Location find_start(const Grid &grid) {
   for (int64_t row{0}; row < grid.size(); ++row) {
     for (int64_t col{0}; col < grid[row].length(); ++col) {
       if (grid[row][col] == 'S') {
-        return Location{row, col};
+        return {row, col};
       }
     }
   }
   throw "unreachable";
 }
 
-int64_t part_1(const Grid &grid) {
-  int64_t ans{0};
+uint64_t part_1(const Grid &grid) {
+  uint64_t ans{0};
   Location start = find_start(grid);
   const auto [start_row, start_col]{start};
   std::set<size_t> cols{};
@@ -67,23 +67,24 @@ int64_t part_1(const Grid &grid) {
   return ans;
 }
 
-void insert_or_increment(std::map<size_t, int64_t> &cols, size_t col,
-                    int64_t value) {
+void insert_or_increment(std::map<size_t, uint64_t> &cols, size_t col,
+                         int64_t value) {
   auto iter = cols.find(col);
   if (iter == cols.end()) {
     cols.insert({col, value});
   } else {
+
     iter->second += value;
   }
 }
 
-int64_t part_2(const Grid &grid) {
+uint64_t part_2(const Grid &grid) {
   Location start = find_start(grid);
   const auto [start_row, start_col]{start};
-  std::map<size_t, int64_t> cols;
-  cols.insert(std::make_pair(start_col, 1));
+  std::map<size_t, uint64_t> cols;
+  cols.insert({start_col, 1});
   for (size_t row{start_row}; row < grid.size(); ++row) {
-    std::map<size_t, int64_t> next_cols;
+    std::map<size_t, uint64_t> next_cols;
     for (auto [col, cnt] : cols) {
       if (at_loc(grid, row, col) == '^') {
         insert_or_increment(next_cols, col - 1, cnt);
@@ -95,6 +96,6 @@ int64_t part_2(const Grid &grid) {
     cols = std::move(next_cols);
   }
   return std::accumulate(
-      cols.begin(), cols.end(), 0ll,
-      [](int64_t acc, auto entry) { return acc + entry.second; });
+      cols.begin(), cols.end(), 0ull,
+      [](const uint64_t acc, const auto &entry) { return acc + entry.second; });
 }