criptmat.cpp: In function 'int main()': criptmat.cpp:7: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result criptmat.cpp:8: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result criptmat.cpp:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result criptmat.cpp:11: warning: ignoring return value of 'char* gets(char*)', declared with attribute warn_unused_result /tmp/ccDQ5izf.o: In function `main': criptmat.cpp:(.text+0x6f): warning: the `gets' function is dangerous and should not be used.