text: #include <stdio.h>
  #include <string.h>
  #include "STACK.c"
  
  main() {
    char *a = "((1+2)*3)";
    int i, N = strlen(a);
    STACKinit(N);
    for (i = 0; i < N; i++) {
      if (a[i] == ')') {
        printf("%c ", STACKpop());
      }
      if ((a[i] == '+') || (a[i] == '*')) {
        STACKpush(a[i]);
      }
      if ((a[i] >= '0') && (a[i] <= '9')) {
        printf("%c ", a[i]);
      }
    }
    printf("\n");
  }
  