#include <bits/stdc++.h>

using namespace std;

#define ll long long
#define MoD 1e9 + 7
#define clear(a) memset(a, 0, sizeof(a))
#define fo(i, a, b) for(int i = a; i < b; i++)
//#define re(i, a, b) for(int i = b; i > a; i--)
#define pb(a) push_back(a)

template<typename T1,typename T2> inline void chmin(T1 &a,T2 b){if(a>b) a=b;}
template<typename T1,typename T2> inline void chmax(T1 &a,T2 b){if(a<b) a=b;}

int a, b, c, d, e, f;

void solve(){
	cin >> a >> b >> c >> d >> e >> f;

	int ra= (c/2)*(c/2)+(d/2)*(d/2)-(e-f);
	cout.precision(20);
	cout << sqrt(ra) << '\n';
}

int main() {
	ios::sync_with_stdio(0);
	cin.tie(0);

	int t=1;
	for(int i=1; i<=t; ++i) {
		solve();
	}

}