像下面的文件a1.txt中的数据，我想读取其中第5行到10行的数据存储到文件a2.txt中，请问如何编程，谢谢！
或是怎样从指定行开始读取数据？

THE BELOW ELEMENT MATRICES AND LOAD VECTORS ARE IN THE NODAL COORDINATE SYSTEMS.
GRAVITY AND TRANSIENT EFFECTS ARE INCLUDED.

STIFFNESS MATRIX FOR ELEMENT 1
1 0.6889000E+10 0.0000000E+00 0.0000000E+00 -0.6889000E+10 0.0000000E+00 0.0000000E+00
2 0.0000000E+00 0.0000000E+00 0.0000000E+00 0.0000000E+00 0.0000000E+00 0.0000000E+00
3 0.0000000E+00 0.0000000E+00 0.0000000E+00 0.0000000E+00 0.0000000E+00 0.0000000E+00
4 -0.6889000E+10 0.0000000E+00 0.0000000E+00 0.6889000E+10 0.0000000E+00 0.0000000E+00
5 0.0000000E+00 0.0000000E+00 0.0000000E+00 0.0000000E+00 0.0000000E+00 0.0000000E+00
6 0.0000000E+00 0.0000000E+00 0.0000000E+00 0.0000000E+00 0.0000000E+00 0.0000000E+00

MASS MATRIX FOR ELEMENT 1