#include <algorithm>
#include <cmath>
#include <iostream>
#include <list>
#include <set>
#include <utility>
#include <vector>

using namespace std;

struct ak {
  long long k;
  long long a;
};

int main() {

  int n;
  cin >> n;
  vector<ak> data(n);

  for(int i = 0; i < n; i++) {
    cin >> data[i].k;
    cin >> data[i].a;
  }

  //From max to min
  sort(data.begin(), data.end(), [](const ak &a, const ak &b){return a.k > b.k;});

  long long r = data[0].k + 1;
  bool allok = false;

  while(!allok) {
    allok = true;
    for(int i = 0; i < n; i++) {
      ak cur = data[i];
      double new_r = log(cur.a)/log(4);
      if( (r-cur.k) < new_r ) {
        allok = false;
        r = (new_r > (r+1) ? new_r : r+1);
        break;
      }
    }
  }

  cout << r;

  return 0;
}