Compilare: user.cpp: In function ‘int main(int, const char**)’: user.cpp:133:34: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for( int i = 0; i < lst.size(); i ++ ) { ^ user.cpp:136:41: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for( int j = 0; j < lst[i].size(); j ++ ) { ^ user.cpp:140:34: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for( int i = 0; i < upd.size(); i ++ ) { ^ user.cpp:142:41: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for( int j = 0; j < upd[i].size(); j ++ ) { ^