Compilare: main.cpp: In function 'void solve()': main.cpp:70:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=1;i<=M&&sol.size()<n-1;++i) ~~~~~~~~~~^~~~ main.cpp:84:12: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0;i<sol.size();++i) ~^~~~~~~~~~~ main.cpp: In function 'int main()': main.cpp:91:9: warning: unused variable 'i' [-Wunused-variable] int i; ^