import java.io.IOException;
import java.io.InputStream;
import java.util.NoSuchElementException;


public class Main {

	public static void main(String[] args) {
		FastScanner sc = new FastScanner();
		long N = sc.nextLong();
		long A = sc.nextLong();
		
		// A * (k - 1) + s^k >= N

		long min = Long.MAX_VALUE;
		for (int k = 1; k <= 100; k ++) {
			long left = 1;
			long right = Long.MAX_VALUE / 3;
			while (left <= right) {
				long s = (left + right) / 2;
				if (check(s, k, N)) {
					right = s - 1;
				} else {
					left = s + 1;
				}
			}
			long s = left;
			int cnt = f(k, s, N, A);
			long time = A * (k - 1) + s * k - cnt;
			min = Math.min(min, time);
		}
		System.out.println(min);
	}
	
	private static boolean check(long s, int k, long N) {
		long v = 1;
		for (int i = 0; i < k; i ++) {
			v *= s;
			if (v < 0 || v >= N) {
				return true;
			}
		}
		return false;
	}
	
	private static int f(int k, long s, long N, long A) {
		long now = 1;
		for (int i = 0; i < k; i ++) {
			now *= s;
		}

		int count = 0;
		while (now >= N) {
			now /= s;
			now *= s - 1;
			count ++;
		}
		
		return count - 1;
	}
}



class FastScanner {
	public static String debug = null;

	private final InputStream in = System.in;
	private int ptr = 0;
	private int buflen = 0;
	private byte[] buffer = new byte[1024];
	private boolean eos = false;

	private boolean hasNextByte() {
		if (ptr < buflen) {
			return true;
		} else {
			ptr = 0;
			try {
				if (debug != null) {
					buflen = debug.length();
					buffer = debug.getBytes();
					debug = "";
					eos = true;
				} else {
					buflen = in.read(buffer);
				}
			} catch (IOException e) {
				e.printStackTrace();
			}
			if (buflen < 0) {
				eos = true;
				return false;
			} else if (buflen == 0) {
				return false;
			}
		}
		return true;
	}

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

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

	private void skipUnprintable() {
		while (hasNextByte() && !isPrintableChar(buffer[ptr]))
			ptr++;
	}

	public boolean isEOS() {
		return this.eos;
	}

	public boolean hasNext() {
		skipUnprintable();
		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() {
		return (int) nextLong();
	}

	public long[] nextLongList(int n) {
		return nextLongTable(1, n)[0];
	}

	public int[] nextIntList(int n) {
		return nextIntTable(1, n)[0];
	}

	public long[][] nextLongTable(int n, int m) {
		long[][] ret = new long[n][m];
		for (int i = 0; i < n; i ++) {
			for (int j = 0; j < m; j ++) {
				ret[i][j] = nextLong();
			}
		}
		return ret;
	}

	public int[][] nextIntTable(int n, int m) {
		int[][] ret = new int[n][m];
		for (int i = 0; i < n; i ++) {
			for (int j = 0; j < m; j ++) {
				ret[i][j] = nextInt();
			}
		}
		return ret;
	}
}

Measured memory_bytes: 8276