triangle.cpp: In function 'int main()':
triangle.cpp:17:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
freopen( "triangles.in", "r", stdin );
~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
triangle.cpp:18:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
freopen( "triangles.out", "w", stdout );
~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~