#include<iostream.h>
#include<math.h>
void main()
{ int n,k,d;
  cin>>n;
  d=1+8*n;
  k=(-1+sqrt(d))/2;
  if(k*(k+1)/2==n) cout<<1;
  else{  k++;
	 cout<<1+k*(k+1)/2-n;
      }
}