Compilare: user.cpp: In function ‘void solve_chains()’: user.cpp:70:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0; i<s.size(); i++) ^ user.cpp: In function ‘void calc(int)’: user.cpp:80:25: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (i=0; i<ch.size(); i++) { ^ user.cpp: In function ‘int main()’: user.cpp:96:12: warning: unused variable ‘j’ [-Wunused-variable] int i, j, x, y; ^