/* -*- coding: utf-8 -*-
 *
 * 3241.cc:  No.3241 Make Multiplication of 8 - yukicoder
 */

#include<cstdio>
#include<algorithm>

using namespace std;

/* constant */

/* typedef */

using ll = long long;

/* global variables */

/* subroutines */

/* main */

int main() {
  int n;
  scanf("%d", &n);

  ll cs[4] = {};
  for (int i = 0; i < n; i++) {
    int ai, bi;
    scanf("%d%d", &ai, &bi);

    int c = 0;
    while (! (ai & 1)) ai >>= 1, c++;

    if (c > 0) cs[min(3, c)] += bi;
  }
  //for (int i = 1; i <= 3; i++) printf(" %lld", cs[i]); putchar('\n');

  ll sum = cs[3];

  ll d = min(cs[1], cs[2]);
  sum += d, cs[1] -= d, cs[2] -= d;

  sum += cs[1] / 3 + cs[2] / 2;

  printf("%lld\n", sum);
  
  return 0;
}