diff --git a/src/day2.cpp b/src/day2.cpp
index 7f936a8..784a348 100644
--- a/src/day2.cpp
+++ b/src/day2.cpp
@@ -13,7 +13,7 @@ struct Data {
 using std::cout, std::endl, std::vector, std::ifstream;
 
 int64_t part_1(const vector<Data> &);
-unsigned long long part_2(const vector<Data> &);
+int64_t part_2(const vector<Data> &);
 
 int main() {
   ifstream file{"input/2025-2.txt"};
@@ -61,8 +61,8 @@ int64_t solve_n(int64_t n) {
   return 0;
 }
 
-unsigned long long part_2(const vector<Data> &v) {
-  unsigned long long ans{0};
+int64_t part_2(const vector<Data> &v) {
+  int64_t ans{0};
   for (auto d : v) {
     for (auto n{d.min}; n <= d.max; ++n) {
       ans += solve_n(n);
@@ -70,7 +70,7 @@ unsigned long long part_2(const vector<Data> &v) {
   }
 
   // todo: dead code, delete me
-  unsigned long long foobar = std::accumulate(v.begin(), v.end(), 0, [&ans](unsigned long long acc, Data d) {
+  int64_t foobar = std::accumulate(v.begin(), v.end(), 0, [&ans](int64_t acc, Data d) {
     for (auto n{d.min}; n <= d.max; ++n) {
           acc += solve_n(n);
     }