Bucket Sort

#include <stdio.h>
void bucketSort(int a[], int max, int min, int n){
    int count = 0;
    int bucket[max - min];
    for(int i = 0; i < max-min+1; i++) bucket[i] = -1;
    for(int i = 0; i<n; i++) bucket[a[i]-min] = a[i];
    for(int i = 0; i < max-min+1; i++)
        if(bucket[i]!=-1)a[count++] = bucket[i];
}
int main(){
    int n, max = 0, min = 0;
    printf("How many elements to insert?: ");
    scanf("%d",&n);
    int a[n];
    printf("Enter %d  elements.", n);
    for(int i = 0; i < n; i++){
        up: scanf("%d", &a[i]);
        if(a[i] == -1){
            printf("Enter elements that aren't -1");
            goto up;
        }
        if(i==0 || max < a[i]) max = a[i];
        if(i==0 || min > a[i]) min = a[i];
    }
    bucketSort(a, max, min, n);
    for(int i = 0; i < n; i++)
        printf("%d ", a[i]);
}