/*masterwayne*/
#include<bits/stdc++.h>
using namespace std;
#define sc(x) scanf("%d",&x)
#define sc2(x,y) scanf("%d %d",&x,&y)
#define sc3(x,y,z) scanf("%d %d %d",&x,&y,&z)
#define pf(x) printf("%d",x)
#define pf2(x,y) printf("%d %d",x,y)
#define pf3(x,y,z) printf("%d %d %d",x,y,z)
#define fr(i,x,n) for(int i=x;i<n;i++)
#define fre(i,x,n) for(int i=x;i<=n;i++)
#define fb(i,x,n) for(int i=n-1;i>=x;i--)
#define fbe(i,x,n) for(int i=n;i>=x;i--)
#define pfn() printf("\n")
#define pfs() printf(" ")
#define pb push_back
long long int n,m,k;
int check(long long int val)
{
	long long int req=val;
	val = val-1;
	int left = k-1;
	int right = n-k;
	if(val<=left)
	{
		long long rem = left-val;
		req+=((val*(val+1)/2)+rem);
	}
	else
	{
		long long temp = val-left;
		long long add = (val*(val+1)/2)-(temp*(temp+1)/2);
		req+=add;
	}
	if(val<=right)
	{
		long long rem = right-val;
		req+=((val*(val+1)/2)+rem);
	}
	else
	{
		long long temp = val-right;
		long long add = (val*(val+1)/2)-(temp*(temp+1)/2);
		req+=add;
	}
	if(req<=m)
		return 1;
	return 0;
}
long long int solve()
{
	long long int l = 1;
	long long int r=m;
	long long int ans = 1;
	while(l<=r)
	{
		int mid = l + (r-l)/2;
		if(check(mid))
		{
			if(ans<mid)
				ans=mid;
			l=mid+1;
		}
		else
			r=mid-1;
	}
	return ans;
}
int main()
{
	cin>>n>>m>>k;
	if(m<n)
	cout<<"0";
    else
	cout<<solve();
	return 0;
}