MOD = 998244353i64 IS_PRIME = Array.new(10_001_001, true) 2.upto(IS_PRIME.size - 1) do |i| if IS_PRIME[i] (i * 2).step(to: IS_PRIME.size - 1, by: i) do |j| IS_PRIME[j] = false end end end PRIMES = (2...IS_PRIME.size).select { |i| IS_PRIME[i] } TWINS = [] of Int32 7.step(to: IS_PRIME.size - 1, by: 4) do |i| if IS_PRIME[i] && IS_PRIME[i - 2] TWINS << i end end read_line.to_i.times do puts solve() end def solve n, m = read_line.split.map(&.to_i) if n == 1 return PRIMES.bsearch_index { |v, _| v > m }.not_nil! end mat = Matrix(Int64).new(3, 3) cnt = TWINS.bsearch_index { |v, _| v > m } || TWINS.size mat.a[1][0] = cnt mat.a[2][0] = cnt mat.a[0][1] = 1 mat.a[0][2] = 1 mat.a[1][2] = 1 mat.a[2][1] = 1 mat = mat.pow(n - 1) ans = 0i64 v = [1, cnt, cnt] 3.times do |i| 3.times do |j| ans += mat.a[i][j] * v[j] end end ans % MOD end class Matrix(T) @a : Array(Array(T)) getter :a, :d1, :d2 def initialize(n : Int32, m : Int32) @a = Array.new(n) { Array.new(m, T.zero) } @d1 = n @d2 = m end def clone ret = Matrix(T).new(@d1, @d2) @d1.times do |i| @d2.times do |j| ret.a[i][j] = @a[i][j] end end return ret end def [](idx : Int32) return @a[idx] end def mul(other : Matrix(T)) if @d2 != other.d1 raise ArgumentError.new end d3 = other.d2 tmp = Array.new(d3) { Array.new(@d2, T.zero) } d3.times do |i| tr1 = tmp[i] @d2.times do |j| tr1[j] = other[j][i] end end ret = Array.new(@d1) { Array.new(d3, T.zero) } @d1.times do |i| row1 = @a[i] ret1 = ret[i] d3.times do |j| sum = T.zero row2 = tmp[j] @d2.times do |k| sum += row1[k] * row2[k] sum %= MOD end ret1[j] = sum end end @a = ret end def mul_l(other : Matrix(T)) # in-place if other.d2 != @d1 raise ArgumentError.new end d3 = @d2 tmp = Array.new(d3) { Array.new(@d1, T.zero) } d3.times do |i| tr1 = tmp[i] @d1.times do |j| tr1[j] = @a[j][i] end end other.d1.times do |i| row1 = other.a[i] ret1 = @a[i] d3.times do |j| sum = T.zero row2 = tmp[j] other.d2.times do |k| sum += row1[k] * row2[k] sum %= MOD end ret1[j] = sum end end end def pow(p : Int64) b = Matrix(T).new(@d1, @d2) ret = Matrix(T).new(@d1, @d2) @d1.times do |i| @d2.times do |j| b.a[i][j] = @a[i][j] % MOD end ret.a[i][i] = 1 end while p > 0 if (p & 1) != 0 ret.mul_l(b) end b.mul(b) p >>= 1 end return ret end end