Compilare: user.cpp: In function ‘int main()’: user.cpp:26:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0;i<a.size();i++) ^ user.cpp:34:24: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0;i<a.size()-1;i++) ^ user.cpp:39:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=a.size()-1;i<b.size();i++) ^ user.cpp:23:11: warning: unused variable ‘j’ [-Wunused-variable] int i,j,ind; ^ user.cpp: In function ‘int to_int(char)’: user.cpp:20:1: warning: control reaches end of non-void function [-Wreturn-type] } ^