#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
int main(){
	ll n,m,k;
	cin>>n>>m>>k;
	m-=n;
	ll  l=0,r=m,h=1;
	while (true){
		if (l==r){
			break;
		}
		ll x=(r+l+1)/2;
		if(x+min(k-1,x-1)*(x-1+max(h,x-(k-1)))/2+min(n-k,x-1)*(x-1+max(x-n+k,h))/2<=m){
			l=x;
		}
		else
		r=x-1;
	}
	cout<<r+1;
	return 0;
}