import java.io.BufferedReader; import java.io.IOException; import java.io.InputStream; import java.io.InputStreamReader; import java.io.OutputStream; import java.io.PrintWriter; import java.util.Arrays; public class Main { public static void main(String[] args) { InputStream inputStream = System.in; OutputStream outputStream = System.out; MyInput in = new MyInput(inputStream); PrintWriter out = new PrintWriter(outputStream); TaskX solver = new TaskX(); solver.solve(1, in, out); out.close(); } static int INF = 1 << 30; static long LINF = 1L << 55; static int MOD = 1000000007; static int[] mh4 = { 0, -1, 1, 0 }; static int[] mw4 = { -1, 0, 0, 1 }; static int[] mh8 = { -1, -1, -1, 0, 0, 1, 1, 1 }; static int[] mw8 = { -1, 0, 1, -1, 1, -1, 0, 1 }; static class TaskX { public void solve(int testNumber, MyInput in, PrintWriter out) { int n = in.nextInt(); long a = in.nextLong(), b = in.nextLong(), w = in.nextLong(); long[] d = in.nextLongArray(n); ConvexHullTrick cht = new ConvexHullTrick(n + 100); long[] dp = new long[n+1]; dp[0] = 0; for (int i = 1; i < n+1; i++) { dp[i] = cht.query(i-1) - (i-1) * a + (long)(i-1) * i / 2 * b + d[i-1]; cht.addLine(-i * b, dp[i] + i * a + (long)(i - 1) * i / 2 * b); } long ans = LINF; for (int i = 0; i < n+1; i++) { ans = Math.min(ans, dp[i] - (n - i) * a + (long)(n - i) * (n - i + 1) / 2 * b); } out.println(w + ans); } /** * 追加クエリの直線の傾きが単調減少の場合 * - insert (a, b): add y = ax + b * - query (x) : min_i{a[i]x + b} * */ class ConvexHullTrick { long[] A, B; int len; public ConvexHullTrick(int n) { A = new long[n]; B = new long[n]; } private boolean check(long a, long b) { return (B[len - 2] - B[len - 1]) * (a - A[len - 1]) >= (B[len - 1] - b) * (A[len - 1] - A[len - 2]); } public void addLine(long a, long b) { while (len >= 2 && check(a, b)) { len--; } A[len] = a; B[len] = b; len++; } public long query(long x) { int l = -1, r = len; while (r - l > 1) { int mid = (r + l) / 2; if (get(mid, x) >= get(mid + 1, x)) { l = mid; } else { r = mid; } } return get(r, x); } private long get(int k, long x) { return A[k] * x + B[k]; } } } static class MyInput { private final BufferedReader in; private static int pos; private static int readLen; private static final char[] buffer = new char[1024 * 8]; private static char[] str = new char[500 * 8 * 2]; private static boolean[] isDigit = new boolean[256]; private static boolean[] isSpace = new boolean[256]; private static boolean[] isLineSep = new boolean[256]; static { for (int i = 0; i < 10; i++) { isDigit['0' + i] = true; } isDigit['-'] = true; isSpace[' '] = isSpace['\r'] = isSpace['\n'] = isSpace['\t'] = true; isLineSep['\r'] = isLineSep['\n'] = true; } public MyInput(InputStream is) { in = new BufferedReader(new InputStreamReader(is)); } public int read() { if (pos >= readLen) { pos = 0; try { readLen = in.read(buffer); } catch (IOException e) { throw new RuntimeException(); } if (readLen <= 0) { throw new MyInput.EndOfFileRuntimeException(); } } return buffer[pos++]; } public int nextInt() { int len = 0; str[len++] = nextChar(); len = reads(len, isSpace); int i = 0; int ret = 0; if (str[0] == '-') { i = 1; } for (; i < len; i++) ret = ret * 10 + str[i] - '0'; if (str[0] == '-') { ret = -ret; } return ret; } public long nextLong() { int len = 0; str[len++] = nextChar(); len = reads(len, isSpace); int i = 0; long ret = 0; if (str[0] == '-') { i = 1; } for (; i < len; i++) ret = ret * 10 + str[i] - '0'; if (str[0] == '-') { ret = -ret; } return ret; } public char nextChar() { while (true) { final int c = read(); if (!isSpace[c]) { return (char) c; } } } public String nextString() { return new String(nextChars()); } public char[] nextChars() { int len = 0; str[len++] = nextChar(); len = reads(len, isSpace); return Arrays.copyOf(str, len); } public char[][] next2DChars(int h, int w) { char[][] s = new char[h][w]; for (int i = 0; i < h; i++) { s[i] = nextChars(); } return s; } int reads(int len, boolean[] accept) { try { while (true) { final int c = read(); if (accept[c]) { break; } if (str.length == len) { char[] rep = new char[str.length * 3 / 2]; System.arraycopy(str, 0, rep, 0, str.length); str = rep; } str[len++] = (char) c; } } catch (MyInput.EndOfFileRuntimeException e) { } return len; } public int[] nextIntArray(final int n) { final int[] res = new int[n]; for (int i = 0; i < n; i++) { res[i] = nextInt(); } return res; } public int[] nextIntArray1Index(final int n) { final int[] res = new int[n + 1]; for (int i = 1; i < n + 1; i++) { res[i] = nextInt(); } return res; } public int[] nextIntArrayDec(final int n) { final int[] res = new int[n]; for (int i = 0; i < n; i++) { res[i] = nextInt() - 1; } return res; } public long[] nextLongArray(final int n) { final long[] res = new long[n]; for (int i = 0; i < n; i++) { res[i] = nextLong(); } return res; } public long[] nextLongArray1Index(final int n) { final long[] res = new long[n + 1]; for (int i = 1; i < n + 1; i++) { res[i] = nextLong(); } return res; } public long[] nextLongArrayDec(final int n) { final long[] res = new long[n]; for (int i = 0; i < n; i++) { res[i] = nextLong() - 1; } return res; } public double nextDouble() { return Double.parseDouble(nextString()); } public double[] nextDoubleArray(int n) { double[] res = new double[n]; for (int i = 0; i < n; i++) { res[i] = nextDouble(); } return res; } static class EndOfFileRuntimeException extends RuntimeException { } } }