Compilare: user.cpp: In function ‘void solve(char*, int&, int&)’: user.cpp:28:26: warning: converting to non-pointer type ‘char’ from NULL [-Wconversion-null] if (p[l-1]=='x'){p[l-1]=NULL;a=atol(p);if (a==0)a=1;n1+=sn*a;} ^ user.cpp: In function ‘int main()’: user.cpp:49:18: warning: format ‘%s’ expects argument of type ‘char*’, but argument 3 has type ‘char (*)[256]’ [-Wformat=] fscanf(f,"%s",&s); ^