/in/foo.cc: In function 'void dfs1(int, int)':
/in/foo.cc:5:37: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
 #define F(i, j, k) for(int i = j; i <= k; ++i)
                                      
/in/foo.cc:27:7:
     F(i, 0, to[x].size()-1) {
       ~~~~~~~~~~~~~~~~~~~~           
/in/foo.cc:27:5: note: in expansion of macro 'F'
     F(i, 0, to[x].size()-1) {
     ^
/in/foo.cc: In function 'bool dfs2(int, int, int)':
/in/foo.cc:5:37: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
 #define F(i, j, k) for(int i = j; i <= k; ++i)
                                      
/in/foo.cc:44:7:
     F(i, 0, to[x].size() - 1) {
       ~~~~~~~~~~~~~~~~~~~~~~         
/in/foo.cc:44:5: note: in expansion of macro 'F'
     F(i, 0, to[x].size() - 1) {
     ^