#include <stdio.h>
#include<string.h>

int main(void) {
    char s1[]="Hello";
    char s2[]="World";

    strcat(s1,s2);
    int s2_len=strlen(s2);

    printf("s1 = %s, s2 = %s and length of s2 = %d.n", s1, s2, s2_len);

    return 0;
}

s1 = HelloWorld, s2 = orld and length of s2 = 4.