import java.io.File;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.Arrays;
import java.util.NoSuchElementException;

public class Main implements Runnable {
	public static void main(String[] args) {
		new Thread(null, new Main(), "", Runtime.getRuntime().maxMemory()).start();
	}

	public void run() {
		Scanner sc = new Scanner();
		int n = sc.nextInt();
		long v = sc.nextLong();
		long[] c = new long[n];
		long[] vol = new long[n];
		long ans = 0;
		long INF = Long.MAX_VALUE / 3;
		for (int i = 0; i < n; ++i) {
			c[i] = sc.nextLong();
			ans += c[i];
			vol[i] = i + 1;
		}
		v -= n;
		for (int i = 1; i < n; ++i) {
			c[i] = c[i] + c[i - 1];
		}
		for (int i = 0; i < n; ++i) {
			for (int j = i + 1; j < n; ++j) {
				if (c[i] * vol[j] > c[j] * vol[i]) {
					c[i] ^= c[j];
					c[j] ^= c[i];
					c[i] ^= c[j];
					vol[i] ^= vol[j];
					vol[j] ^= vol[i];
					vol[i] ^= vol[j];
				}
			}
		}

		if (v >= (long) n * n) {
			long res = v - (long) n * n;
			ans += (res + vol[0] - 1) / vol[0] * c[0];
			v -= (res + vol[0] - 1) / vol[0] * vol[0];
		}

		if (v <= 0) {
			System.out.println(ans);
			return;
		}

		long[] dp = new long[n * n];
		Arrays.fill(dp, INF);
		dp[0] = 0;
		long add = INF;
		for (int i = 0; i < n; ++i) {
			for (int j = (int) v - 1; j >= 0; --j) {
				if (dp[j] == INF)
					continue;
				for (int k = 1;; ++k) {
					if (j + k * vol[i] >= v) {
						add = Math.min(add, dp[j] + k * c[i]);
						break;
					} else {
						dp[j + (int) (k * vol[i])] = Math.min(dp[j + (int) (k * vol[i])], dp[j] + k * c[i]);
					}
				}
			}
		}
		System.out.println(ans + add);

	}

	class Scanner {
		private final InputStream in = System.in;
		private final byte[] buffer = new byte[1024];
		private int ptr = 0;
		private int buflen = 0;

		private boolean hasNextByte() {
			if (ptr < buflen) {
				return true;
			} else {
				ptr = 0;
				try {
					buflen = in.read(buffer);
				} catch (IOException e) {
					e.printStackTrace();
				}
				if (buflen <= 0) {
					return false;
				}
			}
			return true;
		}

		private int readByte() {
			if (hasNextByte())
				return buffer[ptr++];
			else
				return -1;
		}

		private boolean isPrintableChar(int c) {
			return 33 <= c && c <= 126;
		}

		public boolean hasNext() {
			while (hasNextByte() && !isPrintableChar(buffer[ptr]))
				ptr++;
			return hasNextByte();
		}

		public String next() {
			if (!hasNext())
				throw new NoSuchElementException();
			StringBuilder sb = new StringBuilder();
			int b = readByte();
			while (isPrintableChar(b)) {
				sb.appendCodePoint(b);
				b = readByte();
			}
			return sb.toString();
		}

		public long nextLong() {
			if (!hasNext())
				throw new NoSuchElementException();
			long n = 0;
			boolean minus = false;
			int b = readByte();
			if (b == '-') {
				minus = true;
				b = readByte();
			}
			if (b < '0' || '9' < b) {
				throw new NumberFormatException();
			}
			while (true) {
				if ('0' <= b && b <= '9') {
					n *= 10;
					n += b - '0';
				} else if (b == -1 || !isPrintableChar(b)) {
					return minus ? -n : n;
				} else {
					throw new NumberFormatException();
				}
				b = readByte();
			}
		}

		public int nextInt() {
			long nl = nextLong();
			if (nl < Integer.MIN_VALUE || nl > Integer.MAX_VALUE)
				throw new NumberFormatException();
			return (int) nl;
		}

		public double nextDouble() {
			return Double.parseDouble(next());
		}

	}

	static void tr(Object... objects) {
		System.out.println(Arrays.deepToString(objects));
	}
}