String concatenation in c without using strcat ?

 String concatenation in c without using strcat ?  
 #include<stdio.h>  
 #include<conio.h>  
 void main(void)  
 {  
  char s1[25],s2[25];  
  int i=0,k=0;  
  printf("\nEnter First String:");  
  gets(s1);  
  printf("\nEnter Second String:");  
  gets(s2);  
  while(s1[i]!='\0')  
  i++;  
  while(s2[k]!='\0')  
  {  
   s1[i]=s2[k];  
   j++;  
   k++;  
  }  
  s1[i]='\0';  
  printf("\nConcatenated String is %s",s1);  
 }