Compilare: main.cpp: In function 'long long int solve()': main.cpp:67:13: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(it<p.size() && p[it]!=-6) ~~^~~~~~~~~ main.cpp:108:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(it+1==p.size() || p[it+1]==-4) ~~~~^~~~~~~~~~ main.cpp: In function 'int main()': main.cpp:136:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<expr.size();i++) ~^~~~~~~~~~~~ main.cpp:141:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(i<expr.size() && isdigit(expr[i])) ~^~~~~~~~~~~~