#include <iostream>
using namespace std;
#define endl '\n'
 
 
int main() {
   ios::sync_with_stdio(false);
   cin.tie(NULL);
   
   int n, k;
   cin >> n >> k;
 
   int low = 0;
   int high = n;
   long long ret = 0;
   while (low <= high) {
      long long mid = (low + high) / 2;
      ret = (mid * (mid + 1)) / 2 - (n - mid);
      if (ret == k) {
         cout<< n - mid <<endl;
         return 0;
      }
      if (ret > k) {
         high = mid - 1;
      }
      else {
         low = mid + 1;
      }
   }
}