int main(int argc, char **argv) {  
  
    if (argc == 1) {  
        printf("Usage: %s NUM\n", argv[0]);  
        return 1;  
    }  
  
    // Convert the first argument to an integer.  
    int n = strtol(argv[1], NULL, 10);  
  
    for (int i = 0; i < n; i++) {  
        printf("%d", i);  
    }  
    return 0;  
}  