#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using Graph = vector<vector<int>>;
int main() {
  int A1,A2; cin >> A1 >> A2;
  int B1,B2; cin >> B1 >> B2;
  int C,D; cin >> C >> D;
  int x = A2 - C;
  if(x < 0){
    A1 += x;
    B1 -= x;
  }
  int y = B1 - D;
  if(y < 0) {
    A1 += B1;
  }else {
    A1 += D;
  }
  cout << A1 << endl;
}