postmen.cpp: In function 'void dfs(int)':
postmen.cpp:13:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
for (int i = 0; i < a[x].size(); ++i)
~~^~~~~~~~~~~~~
postmen.cpp: In function 'int main()':
postmen.cpp:37:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
for (int i = 0; i < v.size(); ++i)
~~^~~~~~~~~~
postmen.cpp:27:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
scanf("%d%d", &n, &m);
~~~~~^~~~~~~~~~~~~~~~
postmen.cpp:31:14: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
scanf("%d%d", &x, &y);
~~~~~^~~~~~~~~~~~~~~~