foo.cpp: In function 'int main()':
foo.cpp:71:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for(int j=0;j<nw[i].size();j++)
               ~^~~~~~~~~~~~~
foo.cpp:92:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for(int i=0;i<nw[anss].size();i++)
               ~^~~~~~~~~~~~~~~~