#include <bits/stdc++.h>
using namespace std;
 
typedef long long int ll;
typedef unsigned long long int ull;
typedef long double ld;
typedef pair <ll, ll> pll;
typedef pair <int, int> pii;
 
#define pb push_back
#define mp make_pair
#define ff first
#define ss second
#define all(a) a.begin(), a.end()
#define sz(a) (ll)(a.size())
#define endl "\n"
string s;
int n,k;
 
int ans(int l, int r)
{
  	if (r>=l)
		{ 
	  	  long long idx = l + (r - l) / 2; 
		  long long int o= idx*(idx+1)/2;
		
		  if (o-(n-idx)==k)         return idx;
		  else if (o-(n-idx)>k)     return ans(l,idx-1);
		  else                      return ans(idx+1,r);
    	}
 
   return -1;
}
 
int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(NULL); cout.tie(NULL);
 
   cin >> n >> k;
 
   cout<<n-ans(1,n);
   
       return 0;
}