I made a mistake? Where!?!

[98dodgeneondohc]

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
char get_first(void);
int main(void)
{

char line1[40];
char line2[40];
char line3[40];
char ch;
int i;
int j;
int ln;
int logic;
int logic2;
int num1;
int num2;
const char tokseps[]="+-/*";
char * pt, * pt2;

printf("Welcome To The Arithmetic Expression Evaluation Program!");
ch='Y';
while(ch != 'N')
   {
      printf("Enter The Arithmetic Expression:");
      gets(line2);
      j=0;
      for (i=0; i < 40; i++)
      if (!isspace(line2[i]))
            {
               line1[j]=line2[i];
               line3[j]=line2[i];
               j++;
            }


pt=strtok(line1, tokseps);
       pt2=strtok(NULL, tokseps);
       if(pt2==NULL)
       printf("%s Invalid Arithmetic Expression!", line2);
       else
          {
             ln=strlen(pt);
             logic=0;
             for (i=0; i<ln; i++)
                {
                   if (!isdigit(pt[i]))
                   logic=1;
                }
       logic2=0;
       ln=strlen(pt2);
       for (i=0; i < ln; i++)
          {
             if (!isdigit(pt2[i]))
             logic2=1;
          }
       if ((logic==1) || (logic2==1))
       printf("%s Invalid Arithmetic Expression!",line2);
       else
          {
             num1=atoi(pt);
             num2=atoi(pt2);
             ln=strlen(pt);
             if ((line3[ln])=='+')
                printf("the sum of %d and %d is %d.", num1, num2, (num1+num2));
             else if ((line3[ln])=='-')
                printf("the sum of subtraction %d from %d is %d.", num2, num1, (num1-num2));
             else if ((line3[ln])=='*')
                printf("result of multiplication of %d of %d is %d.", num1, num2, (num1*num2));
             else if ((line3[ln]=='/')
{
       if(num2==0)
          printf("error. division by zero!.");
       else
          printf("the result of division %d by %d is %d",num1, num2, (num1/num2));
}
}
}

printf("would you like to continue?");
       ch=get_first();
}
 return 0;
}
       char get_first(void)
{
int ch;
ch=getchar();
while (getchar ()!= '\n')
continue;
return ch;
}

Please someone tell me what's wrong with my program! These braces I put in bold are being highlighted as red when I type them in! I checked and they seem fine! But it's showing as red!

[Dave_Sinkula]

else if ( (line3[ln])=='/' )

[98dodgeneondohc]

else if ( (line3[ln])=='/' )

thanks brotha!!!!