triangle.cpp: In function 'int main()':
triangle.cpp:14:23: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
#define fin(s) freopen( s, "r", stdin )
~~~~~~~^~~~~~~~~~~~~~~~~
triangle.cpp:29:5: note: in expansion of macro 'fin'
fin( "triangles.in" );
^~~
triangle.cpp:15:24: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
#define fout(s) freopen( s, "w", stdout )
~~~~~~~^~~~~~~~~~~~~~~~~~
triangle.cpp:30:5: note: in expansion of macro 'fout'
fout( "triangles.out" );
^~~~