Compilare: user.cpp: In function ‘void read()’: user.cpp:27: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result user.cpp:28: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result user.cpp:31: warning: ignoring return value of ‘char* gets(char*)’, declared with attribute warn_unused_result user.cpp: In function ‘void build(int, int, int)’: user.cpp:55: warning: suggest parentheses around ‘+’ inside ‘>>’ user.cpp:56: warning: suggest parentheses around ‘+’ inside ‘>>’ user.cpp: In function ‘void query(int, int, int)’: user.cpp:68: warning: suggest parentheses around ‘+’ inside ‘>>’ user.cpp:69: warning: suggest parentheses around ‘+’ inside ‘>>’ user.cpp:71: warning: suggest parentheses around ‘+’ inside ‘>>’ user.cpp: In function ‘void update(int, int, int)’: user.cpp:84: warning: suggest parentheses around ‘+’ inside ‘>>’ user.cpp:85: warning: suggest parentheses around ‘+’ inside ‘>>’ user.cpp:86: warning: suggest parentheses around ‘+’ inside ‘>>’ user.cpp:87: warning: suggest parentheses around ‘+’ inside ‘>>’ user.cpp: In function ‘void write()’: user.cpp:133: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result /tmp/ccJUi2gE.o: In function `read()': user.cpp:(.text+0x2a4): warning: the `gets' function is dangerous and should not be used.