How to cut all lines except first and last in string?

Question

C++ / C#

Example string(each new "line" is separated by \n )

0,100,777,555
1,101,777,555
2,102,777,555
3,103,777,555
4,104,777,555
5,105,777,555
6,106,777,555
7,107,777,555
8,108,777,555
9,109,777,555
10,110,777,555
11,111,777,555
18,118,777,555
19,119,777,555
20,120,777,555
21,121,777,555
22,122,777,555
23,123,777,555

Answer 1

something like that:

size_t firstIndex = origString.find_first_of('\n');
size_t lastIndex = origString.find_last_of('\n');
std::string cuttedString = origString.substr(firstIndex, lastIndex - firstIndex)