Regex to check valid Master Card number .
regex = " ^ 5[1-5 ] [ 0-9 ] { 14 } | " + NEW_LINE INDENT " ^ ( 222[1-9 ] ▁ 22[3-9 ] \\d ▁ " + "2[3-6 ] \\d { 2 } ▁ 27[0-1 ] \\d ▁ " + "2720 ) [ 0-9 ] { 12 } $ " NEW_LINE DEDENT