triunghi6.cpp: In function 'int main()': triunghi6.cpp:55: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result triunghi6.cpp:56: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result triunghi6.cpp:58: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result triunghi6.cpp:64: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result triunghi6.cpp:90: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result