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

	
class DJSet {
	int n;
	int[] upper,min,max;
	
	public DJSet(int n) {
		this.n=n;
		upper=new int[n];
		min=new int[n];
		max=new int[n];
		Arrays.fill(upper, -1);
		for (int i=0;i<n;++i) {
			min[i]=i;
			max[i]=i;
		}
	}
	boolean equiv(int x,int y) {
		return root(x)==root(y);
	}
	int root(int x) {
		return upper[x]<0?x:(upper[x]=root(upper[x]));
	}
	int min(int x) {
		return min[root(x)];
	}
	int max(int x) {
		return max[root(x)];
	}
	int sz(int x) {
		return -upper[root(x)];
	}
	void unite(int x,int y) {
		x=root(x);y=root(y);
		if (x==y) return;
		if (upper[x]<upper[y]) {
			x^=y;y^=x;x^=y;
		}
		min[y] =Math.min(min[x],  min[y]);
		max[y]=Math.max(max[x], max[y]);
		upper[y]+=upper[x];
		upper[x]=y;
	}
}

public class Main{
	
	public static void main(String[] args) {
		new Main().run();
	}
	
	void run() {
		FastScanner sc=new FastScanner();
		int L=sc.nextInt();
		int R=sc.nextInt();
		DJSet ds=new DJSet(R+1);
		for (int i=L;i<=R;++i) {
			for (int j=i;j<=R;j+=i) {
				ds.unite(i, j);
			}
		}
		long ans=0;
		for (int i=L;i<=R;++i) {
			if (ds.root(i)==i) {
				++ans;
			}
		}
		--ans;
		System.out.println(ans);
	}
	
	
	void tr(Object...objects) {System.out.println(Arrays.deepToString(objects));}
}

class FastScanner {
    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 static 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());}
}