#include <bits/stdc++.h>
using namespace std;
const long long mod = 998244353;
long long sum[55][100005], f[55][100005], t[100005];
int l[55], r[55];
int add(int p, int x, int y) {
  if (x < 0) return 0;
  if (y < 0) return sum[p][x];
  return sum[p][x] - sum[p][y];
}
long long solve1(int n, int m) {
  long long ans = 0;
  for (int i = l[1]; i <= r[1]; i++) f[1][i] = 1;
  for (int i = 1; i <= m; i++) sum[1][i] = (sum[1][i - 1] + f[1][i]) % mod;
  for (int i = 2; i <= n; i++) {
    for (int j = 1; j <= m; j++) {
      f[i][j] = add(i - 1, j - l[i], j - r[i] - 1);
      sum[i][j] = (sum[i][j - 1] + f[i][j]) % mod;
    }
  }
  for (int i = 1; i <= m; i++) ans = (ans + f[n][i]) % mod;
  for (int i = 1; i <= n; i++)
    for (int j = 1; j <= m; j++) f[i][j] = sum[i][j] = 0;
  return ans;
}
long long solve2(int n, int m, int d) {
  long long ans = 0;
  for (int i = d; i <= m; i += d)
    if (i >= l[1] && i <= r[1]) f[1][i] = 1;
  for (int i = d; i <= m; i += d) sum[1][i] = f[1][i] + sum[1][i - d];
  for (int i = 2; i <= n; i++) {
    for (int j = d; j <= m; j += d) {
      int R = j - l[i] - ((j - l[i]) % d + d) % d;
      int L = j - r[i] - ((j - r[i]) % d + d) % d;
      if ((j - r[i]) % d == 0) L -= d;
      f[i][j] = add(i - 1, R, L);
      sum[i][j] = (sum[i][j - d] + f[i][j]) % mod;
    }
  }
  for (int i = d; i <= m; i += d) ans = (ans + f[n][i]) % mod;
  for (int i = 1; i <= n; i++)
    for (int j = d; j <= m; j += d) f[i][j] = sum[i][j] = 0;
  return ans;
}
int main() {
  int n, m;
  scanf("%d%d", &n, &m);
  for (int i = 1; i <= n; i++) scanf("%d%d", &l[i], &r[i]);
  long long ans = solve1(n, m);
  for (int d = 2; d <= m / n; d++) {
    ans = ((ans - (1 - t[d]) * solve2(n, m, d)) % mod + mod) % mod;
    for (int j = 2; j * d <= m; j++) t[j * d] += 1 - t[d];
  }
  printf("%lld", ans);
  return 0;
}
