Compilare: user.cpp: In function ‘void build(int, int, int)’: user.cpp:18: warning: comparison between signed and unsigned integer expressions user.cpp:29: warning: comparison between signed and unsigned integer expressions user.cpp:29: warning: comparison between signed and unsigned integer expressions user.cpp:42: warning: comparison between signed and unsigned integer expressions user.cpp:44: warning: comparison between signed and unsigned integer expressions user.cpp: In function ‘int main()’: user.cpp:119: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result user.cpp:120: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result user.cpp:121: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result user.cpp:127: warning: ignoring return value of ‘char* gets(char*)’, declared with attribute warn_unused_result user.cpp:191: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result user.cpp:201: warning: ignoring return value of ‘char* gets(char*)’, declared with attribute warn_unused_result /tmp/ccfJROZQ.o: In function `main': user.cpp:(.text+0x832): warning: the `gets' function is dangerous and should not be used.