Not enough valid submissions error

[0x4A-210]

Hi，all
It report Not enough valid submissions error when I use JPlag to detect 2 C source code similarity as below:
version 1:

#include <stdio.h>  

int main() {  

    int n;  

    scanf("%d",&n);  

    n=n*(n+3);  

    printf("%d",n);  

    return 0;  

} 

version 2:

#include <stdio.h>  

int main() {  

    int num;  

    scanf("%d",&num);  

    num=num*num+3*num;  

    printf("%d",num);  

    return 0;  

} 

the two source code above are apparently the same code,but JPlag output the error info below on the terminal:

[Language accepted: C/C++ Scanner [basic markup]
Command line: -l c/c++ -s ./Source -r ./Result
initialize ok
2 submissions
0 submissions parsed successfully!
0 parser errors!
Error: Not enough valid submissions! (only 0 are valid):]

can anyone help me about this problem?