how do i modify this program to

In the following program the inputs are taken randomly
#include<stdio.h>
#include<stdlib.h>
#include<conio.h>
void main()
{
FILE *fp;
int i,n,x,a[45],l=0,m,o,y,z,j;
clrscr();
randomize();
fp=fopen("list1.txt","w");
if(fp==NULL)
{
puts("cannot open file");
exit(0);
}
n=rand()%14;
for(i=1; i<=n; i++)
{
x=rand()%1000;
a[i]=x;
fprintf(fp,"%d\t",x);
}
fclose(fp);

fp=fopen("list2.txt","w");
if(fp==NULL)
{
puts("cannot open file");
exit(0);
}
m=rand()%14;
for(i=1; i<=m; i++)
{
y=rand()%1000;
a[n+i]=y;
fprintf(fp,"%d\t",y);
}
fclose(fp);

fp=fopen("list3.txt","w");
if(fp==NULL)
{
puts("cannot open file");
exit(0);
}
o=rand()%14;
for(i=1; i<=o; i++)
{
z=rand()%1000;
a[n+m+i]=z;
fprintf(fp,"%d\t",z);
}
fclose(fp);
/* reading of first files starts here*/
fp=fopen("list1.txt","r");
if(fp==NULL)
{
puts("cannot open file");
exit(0);
}
printf("\nfirst list:----\n");
while(fscanf(fp,"%d",&x)!=EOF)
printf("%d\t",x);
fclose(fp);
/*reading of second file starts here*/
fp=fopen("list2.txt","r");
if(fp==NULL)
{
puts("cannot open file");
exit(0);
}
printf("\nsecond list:----\n");
while(fscanf(fp,"%d",&y)!=EOF)
printf("%d\t",y);
fclose(fp);
/*reading of third file starts here*/
fp=fopen("list3.txt","r");
if(fp==NULL)
{
puts("cannot open file");
exit(0);
}
printf("\nthird list:----\n");
while(fscanf(fp,"%d",&z)!=EOF)
printf("%d\t",z);
fclose(fp);
printf("\n----------------------------------\n");
/*sorting all elements of array*/
printf("\nfinal sorted list-----------------\n");
for(i=1;i<=n+m+o;i++)
{
for(j=1;j<=n+m+o;j++)
{
if(a[j]>=a[j+1])
{
int temp=a[j+1];
a[j+1]=a[j];
a[j]=temp;
}
}
}
/*storing values in final file*/

fp=fopen("list4.txt","w");
if(fp==NULL)
{
puts("cannot open file");
exit(0);
}
for(i=1; i<=m+n+o; i++)
{
x=a[i];
fprintf(fp,"%d\t",x);
}
fclose(fp);
/*reading final file*/
fp=fopen("list4.txt","r");
if(fp==NULL)
{
puts("cannot open file");
exit(0);
}
while(fscanf(fp,"%d",&x)!=EOF)
printf("%d\t",x);
fclose(fp);
getch();
}

How do we modify this to take input from user
that are 3 list of numbers one by one
then we may get output( merged and sorted list)

#include <stdio.h> #include <stdlib.h> #define lengthof(a) (sizeof (a) / sizeof (*a)) void insertion_sort ( int a[], int n ) { int i; for ( i = 1; i < n; i++ ) { int j, save = a[i]; for ( j = i; j >= 1 && a[j - 1] > save; j-- ) { a[j] = a[j - 1]; } a[j] = save; } } int main ( void ) { int a[45]; int i; // Read the numbers for ( i = 0; i < lengthof ( a ); i++ ) { if ( scanf ( "%d", &a[i] ) != 1 ) { perror ( "Input error" ); return EXIT_FAILURE; } } // Sort the numbers insertion_sort ( a, lengthof ( a ) ); // Print the result for ( i = 0; i < lengthof ( a ); i++ ) { printf ( "%d ", a[i] ); } printf ( "\n" ); return EXIT_SUCCESS; }