Compilare: user.cpp: In function ‘int main()’: user.cpp:111:39: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int k=0; k<S[j].size(); ++k) ^ user.cpp:119:35: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int k=0; k<S[i].size(); ++k) ^ user.cpp:131:35: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int k=0; k<S[i].size(); ++k) ^