balls.cpp: In function 'int main()': balls.cpp:93: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result balls.cpp:94: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result balls.cpp:95: warning: ignoring return value of 'char* gets(char*)', declared with attribute warn_unused_result balls.cpp:96: warning: ignoring return value of 'char* gets(char*)', declared with attribute warn_unused_result balls.cpp: In function 'void backt(int)': balls.cpp:62: warning: 'nc' may be used uninitialized in this function /tmp/ccqvOJHg.o: In function `main': balls.cpp:(.text+0x634): warning: the `gets' function is dangerous and should not be used.