Compilare: main.cpp: In function 'int main()': main.cpp:20:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(j=1;j<=v[a].size();j++) ~^~~~~~~~~~~~~ main.cpp:23:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(j=1;j<=v[a].size();j++) ~^~~~~~~~~~~~~ main.cpp:10:15: warning: unused variable 'b' [-Wunused-variable] int n,i,j,b,a,x; ^