#include <bits/stdc++.h>
using namespace std;
long long i, j, k, n, m, t, l, r, mid;
long long g[600000], inf, b[600000], c[600000], L[600000], R[600000], mi;
inline bool judge() {
  int i, j;
  for (i = 1; i <= r - mid + 1; i++) {
    j = i + mid - 1;
    if (g[j] - g[i] > mi) continue;
    if (L[i] + R[j] <= m) return 1;
  }
  return 0;
}
int main() {
  g[l = r = 0] = 0;
  inf = mi = (long long)1e18 + 10;
  for (; l <= r; l++) {
    long long A = g[l] * 10 + 4;
    if (A < inf) g[++r] = A;
    A += 3;
    if (A < inf) g[++r] = A;
  }
  scanf("%I64d%I64d", &n, &m);
  for (i = 1; i <= n; i++)
    scanf("%I64d%I64d", &b[i], &c[i]), mi = min(c[i] - b[i], mi);
  sort(b + 1, b + n + 1);
  sort(c + 1, c + n + 1);
  sort(g + 1, g + r + 1);
  j = n;
  g[r + 1] = g[r];
  for (i = r; i; i--) {
    long long A = g[i + 1] - g[i];
    if (A && (inf - L[i + 1]) / A < (n - j))
      L[i] = inf;
    else
      L[i] = L[i + 1] + A * (n - j);
    for (; j && b[j] >= g[i]; j--) L[i] = min(L[i] + b[j] - g[i], inf);
  }
  j = 1;
  g[0] = g[1];
  for (i = 1; i <= r; i++) {
    long long A = g[i] - g[i - 1];
    if (A && (inf - R[i - 1]) / A < (j - 1))
      R[i] = inf;
    else
      R[i] = R[i - 1] + A * (j - 1);
    for (; j <= n && c[j] <= g[i]; j++) R[i] = min(R[i] + g[i] - c[j], inf);
  }
  int ll = 1, rr = r;
  for (; ll <= rr;) {
    mid = (ll + rr) / 2;
    if (judge())
      ll = mid + 1;
    else
      rr = mid - 1;
  }
  printf("%d\n", ll - 1);
  return 0;
}
