Compilare: user.cpp: In function ‘int main()’: user.cpp:35:6: warning: unused variable ‘zona3’ [-Wunused-variable] int zona3 = zona2 + nr3; ^~~~~ user.cpp:36:6: warning: unused variable ‘n12’ [-Wunused-variable] int n12, n13, n21, n23, n31, n32; ^~~ user.cpp:36:11: warning: unused variable ‘n13’ [-Wunused-variable] int n12, n13, n21, n23, n31, n32; ^~~ user.cpp:36:16: warning: unused variable ‘n21’ [-Wunused-variable] int n12, n13, n21, n23, n31, n32; ^~~ user.cpp:36:21: warning: unused variable ‘n23’ [-Wunused-variable] int n12, n13, n21, n23, n31, n32; ^~~ user.cpp:36:26: warning: unused variable ‘n31’ [-Wunused-variable] int n12, n13, n21, n23, n31, n32; ^~~ user.cpp:36:31: warning: unused variable ‘n32’ [-Wunused-variable] int n12, n13, n21, n23, n31, n32; ^~~