Compilare: main.cpp: In function 'int main()': main.cpp:27:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(;last[x]<v[x].size();last[x]++) ~~~~~~~^~~~~~~~~~~~ main.cpp:35:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(last[x]==v[x].size()) ~~~~~~~^~~~~~~~~~~~~ main.cpp:38:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(ans.size()!=m+1) ~~~~~~~~~~^~~~~