Compilare: user.cpp: In function ‘void scan(int&)’: user.cpp:18:19: warning: suggest parentheses around ‘&&’ within ‘||’ [-Wparentheses] if('1'<=c && c <= '9' || c == '-') ^ user.cpp:18:11: warning: suggest explicit braces to avoid ambiguous ‘else’ [-Wparentheses] if('1'<=c && c <= '9' || c == '-') ^ user.cpp:21:19: warning: suggest parentheses around ‘&&’ within ‘||’ [-Wparentheses] }while('1'<=c && c <= '9'||c=='-'); ^ user.cpp: In function ‘int main()’: user.cpp:30:9: warning: unused variable ‘a’ [-Wunused-variable] int a; ^