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


public class Main{

	public static void main(String[] args) {
		new Main().run();
	}
	
	final long MOD=(long)1e9+7;
	
	long pow(long a,long n) {
		return n!=0?pow(a*a%MOD,n/2)*(n%2==1?a:1)%MOD:1;
	}
	
	long inv(long a) {
		return pow(a,MOD-2);
	}
	
	int MAX=(int)5e4;
	long[] fac=new long[MAX];
	long[] inv=new long[MAX];
	long[] ifac=new long[MAX];
	{
		fac[0]=ifac[0]=inv[0]=inv[1]=1;
		for (int i=1;i<MAX;++i) {
			fac[i]=i*fac[i-1]%MOD;
		}
		ifac[MAX-1]=inv(fac[MAX-1]);
		for (int i=MAX-2;i>=1;--i) {
			ifac[i]=(i+1)*ifac[i+1]%MOD;			
		}
		for (int i=2;i<MAX;++i) {
			inv[i]=MOD-inv[(int)(MOD%i)]*(MOD/i)%MOD;
		}
	}
	
	long comb(int n,int k) {
		return fac[n]*ifac[k]%MOD*ifac[n-k]%MOD;
	}
	
	long ADD(long a,long b) {
		return a+b>=MOD?a+b-MOD:a+b;
	}
	
	void run() {
		FastScanner sc=new FastScanner();
		long N=sc.nextLong()%MOD;
		int K=sc.nextInt();
		long[] B=new long[K+2];
		B[0]=1;
		for (int i=1;i<K+2;++i) {
			long c=1;
			for (int j=0;j<i;++j) {
//				B[i]+=(j%2==0?-1:1)*comb(i+1,j)*B[j]%MOD;
				B[i]+=(j%2==0?-1:1)*c*B[j]%MOD;
				c=c*inv[j+1]%MOD*(i+1-j)%MOD;
			}
			B[i]=(B[i]%MOD+MOD)%MOD;
			B[i]=B[i]*inv(comb(i+1,i)*(i%2==0?1:MOD-1)%MOD)%MOD;
		}
		long ans=0;
		long pw=N;
		for (int i=1;i<=K+1;++i) {
			ans+=pw*B[K+1-i]%MOD*comb(K+1,i)%MOD;
			pw=pw*N%MOD;
		}
		ans%=MOD;
		ans=ans*inv(K+1)%MOD;
		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());}
}