diff --git a/problem/P1865/P1865.cpp b/problem/P1865/P1865.cpp
new file mode 100644
index 00000000..db2770f6
--- /dev/null
+++ b/problem/P1865/P1865.cpp
@@ -0,0 +1,39 @@
+#include <bits/stdc++.h>
+
+using namespace std;
+
+int ans[10000005];
+
+bool isPrime(int x) {
+    if (x == 1) {
+        return false;
+    }
+    for (int i = 2; i * i <= x; i++) {
+        if (x % i == 0) {
+            return false;
+        }
+    }
+    return true;
+}
+
+int main() {
+    int n, m;
+    cin >> n >> m;
+    for (int i = 1; i <= m; i++) {
+        ans[i] = ans[i - 1];
+        if (isPrime(i)) {
+            ans[i]++;
+        }
+    }
+    while (n--) {
+        int l, r;
+        cin >> l >> r;
+        if (l > m || r > m || l < 1 || r < 1) {
+            cout << "Crossing the line" << endl;
+        }
+        else {
+            cout << ans[r] - ans[l - 1] << endl;
+        }
+    }
+    return 0;
+}