/*
1408 鹽水的故事
Time Limit : 1000 ms  Memory Limit : 32768 K  Output Limit : 256 K

0 MS 300 KB 513 B 
GUN C++
*/

#include <iostream> 
#include <cstdio> 
using namespace std;

double tot, D; 
const double eps = 1.0e-8 ; 

void run() 
{ 
  int ret = 0 ; 
  int sum = 0 ;
  ret = int(tot/D) ;
  if( ret * D + eps <= tot ) 
	ret ++ ;  
  for( int i = 1 ; ; i ++ ) 
  { 
      sum += i ; 
      if( sum >= ret ) 
      { 
          ret += i - 1 ; 
          break; 
      } 
  } 
  cout<<ret<<endl;
} 

int main() 
{ 
  while( cin>>tot>>D )
      run(); 
  return 0; 
}