Untitled

#include <bits/stdc++.h>
using namespace std;

int solve() {
  int n, m;
  cin >> n;
  int v[n], c[n], minv=2000;
  for (int i = 0; i < n; ++i) {
  	scanf("%d,%d", &v[i], &c[i]);
  	minv = min(minv, v[i]);
  }
  cin >> m;
  return min(m, minv*2);
}

int main() {
  cout << solve() << endl;
  return 0;
}