Square pattern in c

I have to make a code to print a square made of stars(*) and its diagonals by inputing the number of lines. For lines=5 it should look like this:square

This is my code so far:

#include <stdio.h>
int main()
{
    int i, j, lines;
    printf("Enter number of lines:");
    scanf("%d",&lines);
         for(i=1; i<=lines; i++)
    {
        for(j=1; j<=lines; j++)
        {
            if(i==1 || i==lines || j==1 || j==lines)
            {
                printf("*");
            }
            else
            {
                printf(" ");
            }
            if(i==j)
            {
                printf(".");
            }
            if(i==(-j))
            {
                printf(".");
            }
        }
        printf("\n");
    }
    return 0;
}