upload

4/A.cpp

@@ -0,0 +1,36 @@
+#include <iostream>
+
+int main() {
+  int n;
+  std::cin >> n;
+
+  int* arr = new int[n];
+
+  for (int i = 0; i < n; ++i) {
+    std::cin >> arr[i];
+  }
+
+  for (int i = 0; i < n; ++i) {
+    if (2 * i + 1 >= n) {
+      break;
+    }
+
+    if (arr[i] > arr[2 * i + 1]) {
+      std::cout << "NO";
+      return 0;
+    }
+
+    if (2 * i + 2 >= n) {
+      break;
+    }
+
+    if (arr[i] > arr[2 * i + 2]) {
+      std::cout << "NO";
+      return 0;
+    }
+  }
+  std::cout << "YES";
+
+  delete[] arr;
+  return 0;
+}