sarpe.cpp: In function 'void dfs(int, int)': sarpe.cpp:19: warning: NULL used in arithmetic sarpe.cpp: In function 'int main()': sarpe.cpp:83: warning: left-hand operand of comma has no effect sarpe.cpp:83: warning: right-hand operand of comma has no effect sarpe.cpp:38: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result sarpe.cpp:39: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result sarpe.cpp:41: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result sarpe.cpp:43: warning: ignoring return value of 'char* gets(char*)', declared with attribute warn_unused_result In file included from /usr/include/stdio.h:910, from /usr/include/c++/4.4/cstdio:45, from sarpe.cpp:1: In function 'char* gets(char*)', inlined from 'int main()' at sarpe.cpp:43: /usr/include/bits/stdio2.h:230: warning: call to '__gets_warn' declared with attribute warning: please use fgets or getline instead, gets can't specify buffer size /tmp/cceN87i6.o: In function `main': sarpe.cpp:(.text+0x575): warning: the `gets' function is dangerous and should not be used.