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

/*allocates memory for concatenation of two input streams*/

char *concatenation(const char *a, const char *b)
{
    size_t len_a = strlen(a);
    size_t len_b = strlen(b);

    char *ret = (char *)malloc(len_a + len_b + 1);
    if(ret == NULL) {
        printf("Insufficient memory!\n");
        return 0;
    }

    for(int i = 0; i < len_a; i++) {
        ret[i] = a[i];
    }

    for(int i = len_a, j = 0; i < len_a + len_b; i++, j++) {
        ret[i] = b[j];
    }

    ret[len_a + len_b] = '\0';
    return 0;
}

int main(int argc, char *argv[])
{
    if(argc != 3) {
        fprintf(stderr,"Invalid argument count!\n");
        return 1;
    }
    char *string = concatenation(argv[1], argv[2]);
    printf("%s\n", string);
    free(string);
    return 0;
}