100 < a < 1000
а = 123; 400; 750 ; 999
10 < a <100
а = 12; 75; 99
1 < a < 10
а = 9; 7
1000 < a < 10000
а = 4000; 9990
100 < a < 1000
а = 123; 400; 750 ; 999
10 < a <100
а = 12; 75; 99
1 < a < 10
а = 9; 7
1000 < a < 10000
а = 4000; 9990