diff --git a/atcoder/abc378b_garbage_collection.cpp b/atcoder/abc378b_garbage_collection.cpp
new file mode 100644
index 0000000..539a0f1
--- /dev/null
+++ b/atcoder/abc378b_garbage_collection.cpp
@@ -0,0 +1,37 @@
+// Vicfred
+// https://atcoder.jp/contests/abc378/tasks/abc378_b
+// math, implementation
+#include <iostream>
+#include <vector>
+
+using namespace std;
+
+int main() {
+  int N;
+  cin >> N;
+  vector<long long> r(N), q(N);
+  for(int i = 0; i < N; ++i) {
+    cin >> r[i] >> q[i];
+  }
+  int Q;
+  cin >> Q;
+  long long t, d;
+  for(int i = 0; i < Q; ++i) {
+    cin >> t >> d;
+    t -= 1;
+    int a = (d / r[t]) * r[t] + q[t];
+    /*
+    cout << "day " << d << endl;
+    cout << "r: " << r[t] << endl;
+    cout << "q: " << q[t] << endl;
+    cout << "a: " << a << endl;
+    */
+    if(d <= a) {
+      cout << a << endl;
+    } else {
+      cout << a + r[t] << endl;
+    }
+    // cout << "======" << endl;
+  }
+  return 0;
+}