Compilare: main.cpp: In function 'int main()': main.cpp:15:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j=0; j<s1.size(); j++) ~^~~~~~~~~~ main.cpp:19:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j=0; j<s2.size(); j++) ~^~~~~~~~~~