#!/usr/bin/ruby

module Enumerable
        #Squeezes the same element. This behaves like C++ unique().
        #To get the similar result to Array#uniq, you need to sort it prior.
        # Calculation order is O(n).
        def squeeze
                r=[]
                cur=nil
                self.each{|e|
                        if r.empty?||cur!=e
                                r<<e
                                cur=e
                        end
                }
                r
        end
end

$memo={}
def cycle(n) $memo[n]||=1.upto(1/0.0){|i|return i if ((10**i)-1)%n==0} end
=begin
a=[[0,0],[0,0],[0,0]]
i=3
while i<10000
	p i
	a[i]=[i%10==5?0:-cycle(i),i]
	a[i]=a[i-2] if (a[i-2]<=>a[i])==-1
	i+=1
	a[i]=a[i-1]
	i+=1
end
a=a.map(&:last)
p a.squeeze
=end
a=[0, 3, 7, 17, 19, 23, 29, 47, 59, 61, 97, 109, 113, 131, 149, 167, 179, 181, 193, 223, 229, 233, 257, 263, 269, 289, 313, 337, 361, 367, 379, 383, 389, 419, 433, 461, 487, 491, 499, 503, 509, 541, 571, 577, 593, 619, 647, 659, 701, 709, 727, 743, 811, 821, 823, 857, 863, 887, 937, 941, 953, 971, 977, 983, 1019, 1021, 1033, 1051, 1063, 1069, 1087, 1091, 1097, 1103, 1109, 1153, 1171, 1181, 1193, 1217, 1223, 1229, 1259, 1291, 1297, 1301, 1303, 1327, 1367, 1381, 1429, 1433, 1447, 1487, 1531, 1543, 1549, 1553, 1567, 1571, 1579, 1583, 1607, 1619, 1621, 1663, 1697, 1709, 1741, 1777, 1783, 1789, 1811, 1823, 1847, 1861, 1873, 1913, 1949, 1979, 2017, 2029, 2063, 2069, 2099, 2113, 2137, 2141, 2143, 2153, 2179, 2207, 2221, 2251, 2269, 2273, 2297, 2309, 2339, 2341, 2371, 2383, 2389, 2411, 2417, 2423, 2447, 2459, 2473, 2539, 2543, 2549, 2579, 2593, 2617, 2621, 2633, 2657, 2663, 2687, 2699, 2713, 2731, 2741, 2753, 2767, 2777, 2789, 2819, 2833, 2851, 2861, 2887, 2897, 2903, 2909, 2927, 2939, 2971, 3011, 3019, 3023, 3137, 3167, 3221, 3251, 3257, 3259, 3299, 3301, 3313, 3331, 3343, 3371, 3389, 3407, 3433, 3461, 3463, 3469, 3527, 3539, 3571, 3581, 3593, 3607, 3617, 3623, 3659, 3673, 3701, 3709, 3727, 3767, 3779, 3821, 3833, 3847, 3863, 3943, 3967, 3989, 4007, 4019, 4051, 4057, 4073, 4091, 4099, 4127, 4139, 4153, 4177, 4211, 4217, 4219, 4229, 4259, 4261, 4327, 4337, 4339, 4349, 4421, 4423, 4447, 4451, 4457, 4463, 4567, 4583, 4651, 4673, 4691, 4703, 4783, 4793, 4817, 4931, 4937, 4943, 4967, 5021, 5059, 5087, 5099, 5153, 5167, 5179, 5189, 5233, 5273, 5297, 5303, 5309, 5381, 5393, 5417, 5419, 5501, 5503, 5527, 5531, 5581, 5623, 5651, 5657, 5659, 5669, 5701, 5737, 5741, 5743, 5749, 5779, 5783, 5807, 5821, 5857, 5861, 5869, 5897, 5903, 5927, 5939, 5981, 6011, 6029, 6047, 6073, 6113, 6131, 6143, 6211, 6217, 6221, 6247, 6257, 6263, 6269, 6287, 6301, 6337, 6343, 6353, 6367, 6389, 6473, 6553, 6571, 6619, 6659, 6661, 6673, 6691, 6701, 6703, 6709, 6737, 6779, 6793, 6823, 6829, 6833, 6857, 6863, 6869, 6899, 6949, 6967, 6971, 6977, 6983, 7019, 7057, 7069, 7103, 7109, 7177, 7193, 7207, 7219, 7229, 7247, 7309, 7349, 7393, 7411, 7433, 7451, 7457, 7459, 7487, 7499, 7541, 7577, 7583, 7607, 7673, 7687, 7691, 7699, 7703, 7727, 7753, 7793, 7817, 7823, 7829, 7873, 7901, 7927, 7937, 7949, 8017, 8059, 8069, 8087, 8171, 8179, 8219, 8233, 8263, 8269, 8273, 8287, 8291, 8297, 8353, 8377, 8389, 8423, 8429, 8447, 8501, 8513, 8537, 8543, 8623, 8647, 8663, 8669, 8699, 8713, 8731, 8741, 8753, 8783, 8807, 8819, 8821, 8861, 8863, 8887, 8971, 9011, 9029, 9059, 9103, 9109, 9137, 9221, 9257, 9341, 9343, 9371, 9377, 9421, 9461, 9473, 9491, 9497, 9539, 9623, 9629, 9697, 9739, 9743, 9749, 9767, 9781, 9811, 9817, 9829, 9833, 9851, 9857, 9887, 9931, 9949, 9967]
gets.to_i.times{
	n=gets.to_i
	p a.take_while{|e|e<n}.last
}
__END__
1
1000