/in/foo.cc: In function 'void SPFAi(int)':
/in/foo.cc:45:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for (int i = 0; i < G[x].size(); i++) {
                   ~~^~~~~~~~~~~~~
/in/foo.cc: In function 'void SPFAa(int)':
/in/foo.cc:69:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for (int i = 0; i < g[x].size(); i++) {
                   ~~^~~~~~~~~~~~~