Compilare: user.cpp: In function ‘int expand(int, int, int)’: user.cpp:23:33: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while (st && dr < s[k].size() && s[k][st] == s[k][dr]) ^ user.cpp: In function ‘int main()’: user.cpp:74:35: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 1; i < s[0].size(); ++i) { ^ user.cpp:79:35: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 1; i < s[1].size(); ++i) { ^ user.cpp:84:35: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 1; i < s[0].size(); ++i) { ^ user.cpp:102:35: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 1; i < s[1].size(); ++i) { ^