atoi(s)
char s[];
{ 
      int i,n,sign;
      for (i=0;s[i]==' ' || s[i]=='\n' || s[i]=='\t';i++) ;
      sign=1;
      if (s[i]=='+' || s[i]=='-')
            sign=(s[i++]=='+') ? 1 : -1;
      for (n=0; s[i] >= '0' && s[i] <= '9'; i++)
            n=10*n+s[i]-'0';
      return(sign*n);
}