Compilare: main.cpp: In function 'int main()': main.cpp:21:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0; i<n.size(); i++) s+=val[n[i]-'0']; ~^~~~~~~~~ main.cpp:28:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0; i<n.size(); i++) { ~^~~~~~~~~ main.cpp:31:29: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(j=i+1; j<n.size(); j++) ~^~~~~~~~~