Compilare: user.cpp: In function ‘void afis()’: user.cpp:13:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=1;i<=n;i++) ^ user.cpp: In function ‘void backt(int)’: user.cpp:19:13: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(k==n+1) ^ user.cpp:22:24: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(st[k]=1;st[k]<=n;st[k]++) ^