#include<bits/stdc++.h>
using namespace std;
long long f(long long n)
{
	long long l=0,r=0x7fffffff,mid,s,p;	
	while(l!=r){
		mid=(l+r)/2;
		s=(long long)mid*(mid+1)/2;
		if(s*2-1<n)l=mid+1;
		else r=mid;
	}
	s=1ll*l*(l+1)/2;
	p=l*2-1;
	if(s*2-1-l>=n)p--;
	return p;
}
int main()
{
	long long n;
	cin>>n;
	cout<<f(n);
	return 0;
}