#include <stdio.h>
#include <string.h>
size_t my_strlen(const char *str) {
    size_t len = 0;
    while (*str++) {
        len++;
    }
    return len;
}

int main() {
    const char *test_string = "Hello, world!";
    size_t length = my_strlen(test_string);


char source[] = "Fabian";
    char destination[100];
strcpy(destination, source);

return 0;
}