Why is the C rand() function returning the same value every time?

I've recently written a little program to test the C rand function found in . I've compiled it twice and ran it a multiple times. On every run, the same output was printed out:

2
2
6
3
5
3

Can someone point out the problem? Here is the code:

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

int pick(int start, int end){
    int num  = ( rand()%end ) + start;
    return num;
}

int main(){

    int i;
    for(i=0; i<6; i++){
        printf("%d\n", pick(1, 6));
    }
    return 0;
}