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.
/*
author: rohit_03012002
*/

import java.util.*;
import java.io.*;
import java.math.*;
import java.io.FileWriter; 
import java.io.IOException; 
public class cf{

static class Pair{
        int u;
        int v;
        Pair(int a,int b){
            u=a;
            v=b;
        
        }

        public boolean equals(Object o) {
            Pair other = (Pair) o;
            return ((u == other.u && v == other.v));
        }

    }


////////////////////////////////////**********Code-Start**********/////////////////////////////////////////////////    
public static void main(String[] args) {
    InputStream inputStream = System.in;
    OutputStream outputStream = System.out;
    if (System.getProperty("ONLINE_JUDGE") == null) {
        try {
            System.setOut(new PrintStream(
                new FileOutputStream("output.txt")));
             sc = new InputReader(new FileInputStream("input.txt"));
        }
        catch (Exception e) {
        }
        // int t=s(0);
        // while(--t>0)
            solve();
    }
     else{
        sc = new InputReader(inputStream);
        pw = new PrintWriter(outputStream);
        // int t=s(0);
        // while(--t>0) 
            solve();
        pw.close();
   }
   

}
// static ArrayList<Arraylist<Integer>>arr=new ArrayList<>();
// static PriorityQueue<Integer> pq=new PriorityQueue<>();

public static void solve() {
   long n=s(0l);
   long m=s(0l);
   if (n <= m) {
           System.out.println(n);
        } else {
            n -= m;
            long l = 0, r = (long)2e9;
            while (l < r) {
                long med = (l + r) / 2;
                long val = med * (med+1) / 2;
                if (val >= n) {
                    r = med;
                } else {
                    l = med+1;
                }
            }
            System.out.println(l+m);
        }
}




 
////////////////////////////////////**********Code-End**********//////////////////////////////////////////////////

// Arrays.sort(a,(c,b)->(c.x==b.x)?c.y-b.y:c.x-b.x); sort the array ont the basis of y if x1==x2
// set precision --> String.format("%.df",ans);  
static int inf=Integer.MAX_VALUE;
static int minf=Integer.MIN_VALUE;
static InputReader sc;
static PrintWriter pw;
static ArrayList<ArrayList<Integer>> adj;
static int mod=1000000007;
static int mod1= 998244353;
static int max(int ...a){int m=a[0];for(int e:a)m=(m>=e)?m:e;return m;}
static int min(int ...a){int m=a[0];for(int e:a)m=(m<=e)?m:e;return m;}
static int abs(int a){return Math.abs(a);}
static long max(long ...a){long m=a[0];for(long e:a)m=(m>=e)?m:e;return m;}
static long min(long ...a){long m=a[0];for(long e:a)m=(m<=e)?m:e;return m;}
static long abs(long a){return Math.abs(a);}
static int ceil(double x){return (int)Math.ceil(x);}
static int floor(double x){return (int)Math.floor(x);}


static void subset(int a[],int n,ArrayList<Integer> arr){
    if(n==a.length){
        System.out.println(arr);
        return;
    }
    ArrayList<Integer> b=new ArrayList<>();
    ArrayList<Integer> c=new ArrayList<>();
    b.addAll(arr);
    c.addAll(arr);
    b.add(a[n]);
    subset(a,n+1,b);
    subset(a,n+1,c);
}


static boolean prime[];
static int smallestFactor[];
static ArrayList<Integer> allPrimes;
static void sieveOfEratosthenes(int n)
{
    prime = new boolean[n+1];
    smallestFactor = new int[n+1];
    allPrimes=new ArrayList<>();
    smallestFactor[1] = 1;
    for(int i=2;i<n;i++) {
        prime[i] = true;
        smallestFactor[i] = i;
    }

    for(int p = 2; p*p <=n; p++)
    {
        if(prime[p])
        {
            smallestFactor[p] = p;
            for(int i = p*p; i <= n; i += p) {
                prime[i] = false;
                smallestFactor[i] = Math.min(p,smallestFactor[i]);
            }
        }
    }

    for(int i=0;i<prime.length;i++){
        if(prime[i]){
            allPrimes.add(i);
        }
    }

}
// static void initial(int n){
//    for(int i=0;i<=n;i++){
//        arr.add(new ArrayList<>());
//    }
// }
static int numSum(int n){
  int sum=0;
  while(n!=0){
    sum+=n%10;
    n/=10;
  }
  return sum;
}
static void sort(ArrayList<Integer> brr){
    Collections.sort(brr);
}
static void Lsort(ArrayList<Long> arr){
    Collections.sort(arr);
}
static void sort(int[] a) {
    ArrayList<Integer> l=new ArrayList<>();
    for (int i:a) l.add(i);
    Collections.sort(l);
    for (int i=0; i<a.length; i++) a[i]=l.get(i);
}
static void sort(long[] a) {
        ArrayList<Long> l=new ArrayList<>();
        for (Long i:a) l.add(i);
        Collections.sort(l);
        for (int i=0; i<a.length; i++) a[i]=l.get(i);
}


static boolean isperfect(double number)    
{   
    double sqrt=Math.sqrt(number);  
    return ((sqrt - Math.floor(sqrt)) == 0);   
}   

static boolean isPrime(long n){
    if(n<2){
        return false;
    }
    for(int i = 2; i*i<=n; i++){
        if(n%i==0){
            return false;
        }
    }
    return true;
}
static int lowerBound(int[] arr, int low, int high, long element) {
    int middle;
    while (low < high) {
        middle = low + (high - low) / 2;
        if (element > arr[middle])
            low = middle + 1;
        else
            high = middle;
    }
    if (low < arr.length && arr[low] < element)
        return -1;
    return low;
}

static  int upperBound(int[] arr, int low, int high, long element) {
    int middle;
    while (low < high) {
        middle = low + (high - low) / 2;
        if (arr[middle] > element)
            high = middle;
        else
            low = middle + 1;
    }
    if (low<arr.length &&arr[low] <= element)
        return -1;
    return low;
}

public static String sortString(String inputString) 
{ 
    char tempArray[] = inputString.toCharArray(); 
    Arrays.sort(tempArray); 
    return new String(tempArray); 
} 

public static int ask(int l, int r){
    System.out.println("? "+l+" "+r);
    System.out.flush();
    return sc.nextInt();
}
public static void swap(char []chrr, int i, int j){
    char temp=chrr[i];
    chrr[i]=chrr[j];
    chrr[j]=temp;
}
public static void swap(int []chrr, int i, int j){
    int temp=chrr[i];
    chrr[i]=chrr[j];
    chrr[j]=temp;
}
public static int countSetBits(int n){
    int a=0;
    while(n>0){
        a+=(n&1);
        n>>=1;
    }
    return a;
}
public static boolean isPowerOfTwo(long x){
    return x!=0 && ((x&(x-1)) == 0);
}

static int gcd(int a, int b)
{
  if (b == 0)
    return a;
  return gcd(b, a % b);
}
public static int lcm(int a , int b )
{
    int gc = gcd(a,b);
    return (a/gc)*b;
}
static long fast_pow(long base,long n,long M){
    if(n==0)
       return 1;
    if(n==1)
    return base;
    long halfn=fast_pow(base,n/2,M);
    if(n%2==0)
        return ( halfn * halfn ) % M;
    else
        return ( ( ( halfn * halfn ) % M ) * base ) % M;
}
static long modInverse(long n,long M){
    return fast_pow(n,M-2,M);
}
public static String reverse(String input)
{
    StringBuilder str  = new StringBuilder("") ;

    for(int i =input.length()-1 ; i >= 0  ; i-- )
    {
        str.append(input.charAt(i));
    }

    return str.toString() ;
}

public static long nCr(int n,int k)
{
    long ans=1L;
    k=k>n-k?n-k:k;
    int j=1;
    for(;j<=k;j++,n--)
    {
        if(n%j==0)
        {
            ans*=n/j;
        }else
        if(ans%j==0)
        {
            ans=ans/j*n;
        }else
        {
            ans=(ans*n)/j;
        }
    }
    return ans;
}
public static long kadanesAlgorithm(long[] arr)
{

    if(arr.length == 0)return  0 ;
    
      long[] dp = new long[arr.length] ;
      
      dp[0] = arr[0] ;
      long max =  dp[0] ;
      
      
      for(int i = 1; i <  arr.length ; i++)
      {
            if(dp[i-1] > 0)
            {
                  dp[i] = dp[i-1] + arr[i] ;
            }
            else{
                  dp[i] = arr[i] ;
            }
            
            if(dp[i] >  max)max = dp[i] ;
            
      }
      
      return max  ;
  
}

private static int countDigits(int l) {
        if (l >= 1000000000) return 10;
        if (l >= 100000000) return 9;
        if (l >= 10000000) return 8;
        if (l >= 1000000) return 7;
        if (l >= 100000) return 6;
        if (l >= 10000) return 5;
        if (l >= 1000) return 4;
        if (l >= 100) return 3;
        if (l >= 10) return 2;
        return 1;
    }

    private static int countDigits(long l) {
        if (l >= 1000000000000000000L) return 19;
        if (l >= 100000000000000000L) return 18;
        if (l >= 10000000000000000L) return 17;
        if (l >= 1000000000000000L) return 16;
        if (l >= 100000000000000L) return 15;
        if (l >= 10000000000000L) return 14;
        if (l >= 1000000000000L) return 13;
        if (l >= 100000000000L) return 12;
        if (l >= 10000000000L) return 11;
        if (l >= 1000000000L) return 10;
        if (l >= 100000000L) return 9;
        if (l >= 10000000L) return 8;
        if (l >= 1000000L) return 7;
        if (l >= 100000L) return 6;
        if (l >= 10000L) return 5;
        if (l >= 1000L) return 4;
        if (l >= 100L) return 3;
        if (l >= 10L) return 2;
        return 1;
    }   
public static int s(int n){
    return sc.nextInt();
}
public static long s(long n){
    return sc.nextLong();
}
public static String s(String n){
    return sc.next();
}
public static double s(double n){
    return sc.nextDouble();
}
public static void p(int n){
    pw.print(n);
}
public static void p(long n){
    pw.print(n);
}
public static void p(String n){
    pw.print(n);
}
public static void p(double n){
    pw.print(n);
}
public static void pln(int n){
    pw.println(n);
}
public static void pln(long n){
    pw.println(n);
}
public static void pln(String n){
    pw.println(n);
}
public static void pln(double n){
    pw.println(n);
}
public static void feedArr(long []arr){
    for(int i=0;i<arr.length;++i)
        arr[i]=sc.nextLong();
}
public static void feedArr(double []arr){
    for(int i=0;i<arr.length;++i)
        arr[i]=sc.nextDouble();
}
public static void feedArr(int []arr){
    for(int i=0;i<arr.length;++i)
        arr[i]=sc.nextInt();
}
public static void feedArr(String []arr){
    for(int i=0;i<arr.length;++i)
        arr[i]=sc.next();
}
public static String printArr(int []arr){
    StringBuilder sbr=new StringBuilder();
    for(int i:arr)
        sbr.append(i+" ");
    return sbr.toString();
}
public  static String printArr(long []arr){
    StringBuilder sbr=new StringBuilder();
    for(long i:arr)
        sbr.append(i+" ");
    return sbr.toString();
}
public static String printArr(String []arr){
    StringBuilder sbr=new StringBuilder();
    for(String i:arr)
        sbr.append(i+" ");
    return sbr.toString();
}
public static String printArr(double []arr){
    StringBuilder sbr=new StringBuilder();
    for(double i:arr)
        sbr.append(i+" ");
    return sbr.toString();
}
static class InputReader {
    public BufferedReader reader;
    public StringTokenizer tokenizer;

    public InputReader(InputStream stream) {
        reader = new BufferedReader(new InputStreamReader(stream), 32768);
        tokenizer = null;
    }
    public String next() {
        while (tokenizer == null || !tokenizer.hasMoreTokens()) {
            try {
                tokenizer = new StringTokenizer(reader.readLine());
            } catch (IOException e) {
                throw new RuntimeException(e);
            }
        }
        return tokenizer.nextToken();
    }
    public int nextInt() {
        return Integer.parseInt(next());
    }
    public long nextLong() {
        return Long.parseLong(next());
    }
    public double nextDouble() {
        return Double.parseDouble(next());
    }
}
}


// smallest lcm(a,b) => a+b=n will be n/smallPrimefactor ans n-(n/smallestprimefactor).
