Program in C to insert a sub-string in to given main string from a given position

Write a C program that uses functions to perform the following operations: 
1. To insert a sub-string in to given main string from a given position

#include <stdio.h>

#include <conio.h>

#include <string.h>

void main()

{

            char a[10];

            char b[10];

            char c[10];

            int p=0,r=0,i=0;

            int t=0;

            int x,g,s,n,o;

            clrscr();

            puts("Enter First String:");

            gets(a);

            puts("Enter Second String:");

            gets(b);

            printf("Enter the position where the item has to be inserted: ");

            scanf("%d",&p);

            r = strlen(a);

            n = strlen(b);

            i=0;

            // Copying the input string into another array

            while(i <= r)

            {

                         c[i]=a[i];

                         i++;

            }

            s = n+r;

            o = p+n;

            // Adding the sub-string

            for(i=p;i<s;i++)

            {

                        x = c[i];

                        if(t<n)

                        {

                                    a[i] = b[t];

                                    t=t+1;

                        }

                        a[o]=x;

                        o=o+1;

            }

            printf("%s", a);

            getch();

}