Compilare: user.cpp: In function ‘int main()’: user.cpp:15:28: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < s.size(); ++i) ^ user.cpp:20:29: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < s.size(); ++i) ^ user.cpp:25:29: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < s.size(); ++i) ^ user.cpp:26:30: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j = i; j < s.size(); ++j) ^ user.cpp:30:30: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int l = 2; l <= s.size(); ++l) { ^ user.cpp:31:40: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i + l - 1 < s.size(); ++i) { ^