public string funcion(string cadena)
{
string cadenafinal="";
char[] ArrayA = cadena.ToCharArray();
char[] ArrayB={'+','-','/','*'};
foreach(char[] item in ArrayA)
{
foreach(char[] itemB in ArrayB)
{
if(item==itemB)
{
}
else
{
cadenafinal+=arrayB[i].toString();
break;
}
}
return cadenafinal;