No long names allowed.

#include <string.h>

int main(int argc, char *argv[]){
unsigned short s;
int i;
char buf[80];

if(argc < 3){
return -1;
}

i = atoi(argv[1]);
s = i;

if(s >= 80){
printf("We dont allow big names.\n");
return -1;
}

strncpy(buf, argv[2], i);
printf("%s\n", buf);
return 0;
}

After compiling, execute it following way:
$ ./a.out 81 alpha0
We dont allow big names.
$./a.out 79 alpha0
alpha0