diff --git a/AtCoder/ABC309/C/C.cpp b/AtCoder/ABC309/C/C.cpp
new file mode 100644
index 00000000..8f80c5b6
--- /dev/null
+++ b/AtCoder/ABC309/C/C.cpp
@@ -0,0 +1,56 @@
+#include <iostream>
+#include <algorithm>
+#include <numeric>
+#include <utility>
+#include <vector>
+
+using std::cin;
+using std::cout;
+const char endl = '\n';
+
+const int N = 3e5 + 5;
+
+int n, k;
+std::pair<int, int> a[N];
+std::vector<int> nums;
+
+int main() {
+    std::ios::sync_with_stdio(false);
+    cin.tie(nullptr);
+
+    cin >> n >> k;
+
+    for (int i = 1; i <= n; i++) {
+        cin >> a[i].first >> a[i].second;
+
+        nums.emplace_back(a[i].first);
+    }
+
+    std::sort(a + 1, a + 1 + n, [](std::pair<int, int> x, std::pair<int, int> y) { return x.first < y.first; });
+    std::sort(nums.begin(), nums.end());
+    nums.erase(std::unique(nums.begin(), nums.end()), nums.end());
+
+    for (int i = 1; i <= n; i++) {
+        a[i].first = std::lower_bound(nums.begin(), nums.end(), a[i].first) - nums.begin() + 1;
+    }
+
+    long long sum = std::accumulate(a + 1, a + 1 + n, 0ll, [](long long x, std::pair<int, int> y) { return x + y.second; });
+
+    if (sum <= k) {
+        cout << 1 << endl;
+
+        exit(0);
+    }
+
+    for (int i = 1; i <= n; i++) {
+        sum -= a[i].second;
+
+        if (sum <= k) {
+            cout << nums[a[i].first - 1] + 1 << endl;
+
+            exit(0);
+        }
+    }
+
+    return 0;
+}