String concatenation without using strcat library function

Given two strings, merge the two strings into a single string.

#include <stdio.h>
#include<string.h>
#include<stdlib.h>
int main(void) {
   char *s,*v;
   int len,i;
   s=(char*)malloc(sizeof(char));
   v=(char*)malloc(sizeof(char));
   scanf("%s",s);
   scanf("%s",v);
   len=strlen(s);
   i=len;
   while(*v)
   {
     *(s+i)=*v;
     i++;
     v++;
   }
   *(s+i)='\0';
   printf("%s",s);
   return 0;
}