from math import factorial compress = lambda arr: {e: i for i, e in enumerate(sorted(set(arr)))} compress2 = lambda arr: {i: e for i, e in enumerate(sorted(set(arr)))} MOD = 998244353 n = int(input()) b = [0] * n c = [0] * n l = [] for i in range(n): b[i], c[i] = map(int, input().split()) b[i] -= 1 l.append(b[i]) l.append(c[i]) cp = compress(l) cp2 = compress2(l) # ans = 0 # for j in range(n): # for k in range(j + 1, n): # ans += (1 - max(0, min(c[j] - b[j], c[k] - b[k], c[j] - b[k], c[k] - b[j]) + 1) * pow((c[j] - b[j] + 1) * (c[k] - b[k] + 1), MOD - 2, MOD)) * f % MOD ans = 0 m = len(cp) w = [0] * m x = [0] * m y = [0] * m for j in range(n): w[cp[b[j]]] += 1 w[cp[c[j]]] -= 1 x[cp[b[j]]] += pow(c[j] - b[j], MOD - 2, MOD) x[cp[c[j]]] -= pow(c[j] - b[j], MOD - 2, MOD) y[cp[b[j]]] += pow((c[j] - b[j]) ** 2, MOD - 2, MOD) y[cp[c[j]]] -= pow((c[j] - b[j]) ** 2, MOD - 2, MOD) s0 = 0 s = 0 s2 = 0 f = 1 for i in range(n - 2): f *= (i + 1) f %= MOD for j in range(m - 1): s0 += w[j] s += x[j] s2 += y[j] ans += (s ** 2 - s2) * pow(2, MOD - 2, MOD) * (cp2[j + 1] - cp2[j]) print(((n * (n - 1) // 2 - ans) * n * (n - 1) // 2) * f % MOD)