Anton likes to listen to fairy tales, especially when Danik, Anton's best friend, tells them. Right now Danik tells Anton a fairy tale:

"Once upon a time, there lived an emperor. He was very rich and had much grain. One day he ordered to build a huge barn to put there all his grain. Best builders were building that barn for three days and three nights. But they overlooked and there remained a little hole in the barn, from which every day sparrows came through. Here flew a sparrow, took a grain and flew away..."

More formally, the following takes place in the fairy tale. At the beginning of the first day the barn with the capacity of n grains was full. Then, every day (starting with the first day) the following happens:

  * m grains are brought to the barn. If m grains doesn't fit to the barn, the barn becomes full and the grains that doesn't fit are brought back (in this problem we can assume that the grains that doesn't fit to the barn are not taken into account). 
  * Sparrows come and eat grain. In the i-th day i sparrows come, that is on the first day one sparrow come, on the second day two sparrows come and so on. Every sparrow eats one grain. If the barn is empty, a sparrow eats nothing. 



Anton is tired of listening how Danik describes every sparrow that eats grain from the barn. Anton doesn't know when the fairy tale ends, so he asked you to determine, by the end of which day the barn will become empty for the first time. Help Anton and write a program that will determine the number of that day!

Input

The only line of the input contains two integers n and m (1 ≤ n, m ≤ 1018) — the capacity of the barn and the number of grains that are brought every day.

Output

Output one integer — the number of the day when the barn will become empty for the first time. Days are numbered starting with one.

Examples

Input

5 2


Output

4


Input

8 1


Output

5

Note

In the first sample the capacity of the barn is five grains and two grains are brought every day. The following happens:

  * At the beginning of the first day grain is brought to the barn. It's full, so nothing happens. 
  * At the end of the first day one sparrow comes and eats one grain, so 5 - 1 = 4 grains remain. 
  * At the beginning of the second day two grains are brought. The barn becomes full and one grain doesn't fit to it. 
  * At the end of the second day two sparrows come. 5 - 2 = 3 grains remain. 
  * At the beginning of the third day two grains are brought. The barn becomes full again. 
  * At the end of the third day three sparrows come and eat grain. 5 - 3 = 2 grains remain. 
  * At the beginning of the fourth day grain is brought again. 2 + 2 = 4 grains remain. 
  * At the end of the fourth day four sparrows come and eat grain. 4 - 4 = 0 grains remain. The barn is empty. 



So the answer is 4, because by the end of the fourth day the barn becomes empty.
import java.io.*;
import java.math.BigInteger;
import java.util.*;
 
 
 
 public class Main {
	public static InputReader in;
    public static PrintWriter pw;
 
 
 
	public static void main(String args[]) {
		new Thread(null, new Runnable() {
            public void run() {
                try{
                    solve();
                }
                catch(Exception e){
                    e.printStackTrace();
                }
            }
        }, "1", 1 << 26).start();
    }
	static ArrayList<Integer> g[];
	static ArrayList<Integer> h[];
	static boolean visited[];
	static boolean visit[];
	static int par[];
	static int degree[];
	static int edjes=0;
	static int start=-1;
	static int end=-1;
	static int Total=0;
	static int time1[];
	static int time2[];
	static int glob=0;
	static int ans[];
	static boolean vis2[][];
	//static long sum1=0;
	//static long val[];
    static ArrayList<Integer> levels[];
    static int max=0;
    static int lev=1;
    static ArrayList<Integer> nodes[];
    static ArrayList<Integer> values[];
    static int depth[];
    static boolean found=false;
   // static long sm[];
    static int sum1=0;
    static int pre[][];
    static int subtree[];
   static  int mn=1000001;
   static  HashMap<String,Integer> hm;
   static int sm[];
   static int dist[];
    static Stack<Integer> tt=new Stack();
    public static void solve(){
		
	
		 in = new InputReader(System.in);
		 pw = new PrintWriter(System.out);
    //long n=in.nextLong();
    long n=in.nextLong();
	long m=in.nextLong();
	if(n<=m){
		System.out.println(n);
	}else{
		
		long low= 0;
		long high= (long)2e9;
		long ans=-1;
		while(low<=high){
			long mid=(low+high)/2;
			long calc= ((mid*(mid+1))) ;
		//pw.println(calc);	
			if(calc>= 2*(n-m)){
				ans=mid;
				high=mid-1;
			}else{
				low=mid+1;
			}
		}
		System.out.println(ans+m);
	}
	}



	public static int countNumber(int n)
    {
        int result = 0;
     
        // Pushing 1 to 9 because all number from 1
        // to 9 have this propert.
        for (int i = 1; i <= 9; i++)
        {
            Stack<Integer> s=new Stack();
            if (i <= n)
            {
                s.push(i);
                result++;
            }
     
            // take a number from stack and add
            // a digit smaller than last digit
            // of it.
            while (!s.empty())
            {
                int tp = s.peek();
                s.pop();
                for (int j = tp%10; j <= 9; j++)
                {
                    int x = tp*10 + j;
                 //   System.out.println(x);
                    if (x <= n)
                    {
                        s.push(x);
                        result++;
                    }
                }
              //  System.out.println();
            }
        }
     
        return result;
    }
    public static boolean IsPrime(long l) {
		// Corner cases
		if (l <= 1)
			return false;
		if (l <= 3)
			return true;
 
		// This is checked so that we can skip 
		// middle five numbers in below loop
		if (l % 2 == 0 || l % 3 == 0)
			return false;
 
		for (long i = 5; i * i <= l; i = i + 6)
			if (l % i == 0 || l % (i + 2) == 0)
				return false;
 
		return true;
	}
 
     
        
     
        

   
/*public static void dfs2(int curr,int lev)
{
	time1[curr]=glob++;
	
	depth[curr]=lev;
	visited[curr]=true;
	nodes[lev].add(time1[curr]);
	values[lev].add(a[curr]);
	for(int x:g[curr])
	{
		if(!visited[x])
		{
			dfs2(x,lev+1);
		}
	}
time2[curr]=glob++;
}
 
 
 
public static void bfs1(int curr)
{
Queue<Integer> Q=new LinkedList<Integer>();
Q.add(1);
visit[1]=true;
int lev=2;
levels[1].add(1);
while(!Q.isEmpty())
{
	int cnt=Q.size();
	while(cnt>0)
	{
		int p=Q.poll();
		visit[p]=true;
		for(int x:g[p])
		{
			if(!visit[x])
			{
				Q.add(x);
				levels[lev].add(x);
			}
		}
		cnt--;
	}
	max=Math.max(lev, max);
	lev++;
}
}
 
 
	
 	private static long fact(int len) {
	long ans=1;
	for(int i=1;i<=len;i++)
		ans*=i;
	return ans;
}
 
 
 
	
	// SubTree Checker DFS (TO CHECK IF X IS IN A SUBTREE OF Y)
	public static void dfs3(int curr)
	{
		visited[curr]=true;
		time1[curr]=glob++;
		for(int x:g[curr])
		{
		if(!visited[x])
			dfs3(x);
		}
		time2[curr]=glob++;
	}
    
	
	
 
    /*NO OF EDJES IN WHOLE CONNECTED COMPONENTS
  
	public static void dfs1(int curr)
	{
		visited[curr]=true;
		for(int next:g[curr])
		{
			edje++;
			if(!visited[next])
				dfs1(next);
		}
	}
	/*SUM OF ALL SUBTREE NODE'S VLAUES DFS
	public static void dfs(int curr,int prev)
		{
		val[curr]=1;
			for(int x:g[curr])
			{
				if(x!=prev)
				{
		            dfs(x,curr);
		            val[curr]+=val[x];
					
			    }
			}
		}*/
	
		public static long power(long a,long b)
		{
			long result=1;
			while(b>0)
			{
				if(b%2==1)
					result*=a;
				a=a*a;
				b/=2;
			}
			return result;
		}
				public static long pow(long n,long p,long m)
	{
		 long  result = 1;
		  if(p==0)
		    return 1;
		if (p==1)
		    return n;
		while(p!=0)
		{
		    if(p%2==1)
		        result *= n;
		    if(result>=m)
		    result%=m;
		    p >>=1;
		    n*=n;
		    if(n>=m)
		    n%=m;
		}
		return result;
	}
	static class Pair implements Comparable<Pair>{
	long now;
		int aft;
		Pair(long l,int weight){
	     	this.now=l;
			this.aft=weight;
			
		}
		@Override
		public int compareTo(Pair o) {
		if(o.now>this.now)
			return 1;
		else
			return -1;
		}
				
	}
	public static long gcd(long a, long b) {
		  if (b == 0) return a;
		  return gcd(b, a%b);
		}
	static class InputReader {
 
		private InputStream stream;
		private byte[] buf = new byte[8192];
		private int curChar, snumChars;
		private SpaceCharFilter filter;
 
		public InputReader(InputStream stream) {
			this.stream = stream;
		}
 
		public int snext() {
			if (snumChars == -1)
				throw new InputMismatchException();
			if (curChar >= snumChars) {
				curChar = 0;
				try {
					snumChars = stream.read(buf);
				} catch (IOException e) {
					throw new InputMismatchException();
				}
				if (snumChars <= 0)
					return -1;
			}
			return buf[curChar++];
		}
 
		public   int nextInt() {
			int c = snext();
			while (isSpaceChar(c))
				c = snext();
			int sgn = 1;
			if (c == '-') {
				sgn = -1;
				c = snext();
			}
			int res = 0;
			do {
				if (c < '0' || c > '9')
					throw new InputMismatchException();
				res *= 10;
				res += c - '0';
				c = snext();
			} while (!isSpaceChar(c));
			return res * sgn;
		}
 
		public long nextLong() {
			int c = snext();
			while (isSpaceChar(c))
				c = snext();
			int sgn = 1;
			if (c == '-') {
				sgn = -1;
				c = snext();
			}
			long res = 0;
			do {
				if (c < '0' || c > '9')
					throw new InputMismatchException();
				res *= 10;
				res += c - '0';
				c = snext();
			} while (!isSpaceChar(c));
			return res * sgn;
		}
 
		public int[] nextIntArray(int n) {
			int a[] = new int[n];
			for (int i = 0; i < n; i++)
				a[i] = nextInt();
			return a;
		}
 
		public String readString() {
			int c = snext();
			while (isSpaceChar(c))
				c = snext();
			StringBuilder res = new StringBuilder();
			do {
				res.appendCodePoint(c);
				c = snext();
			} while (!isSpaceChar(c));
			return res.toString();
		}
 
		public boolean isSpaceChar(int c) {
			if (filter != null)
				return filter.isSpaceChar(c);
			return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
		}
 
		public interface SpaceCharFilter {
			public boolean isSpaceChar(int ch);
		}
	}
}