'commit'

TangDou/LanQiaoBei/LanQiao12ShengSai/BC2_1.cpp

@@ -0,0 +1,13 @@
+#include <bits/stdc++.h>
+
+const int N = 30;
+int a[N] = {2};
+using namespace std;
+
+int main() {
+    int n;
+    cin >> n;
+    for (int i = 1; i <= n; ++i) a[i] = a[i - 1] + pow(2, i - 1);
+    printf("%d", a[n]);
+    return 0;
+}