#include <iostream>
#include <cstdio>
#include <cstring>
using namespace std;
 
int main() {
	int t, n, a[100002], min, max, gap, b[100002];
	scanf("%d", &t);
	while(t--) {
		max=0; min=1000000; gap=0;
		memset(b, 0, sizeof(b));
		scanf("%d", &n);
		for(int i=0; i<n; i++) {
			scanf("%d", &a[i]);
			if(a[i]<min) {
				min=a[i];
				max=a[i];
			}
			else if(a[i]>max) {
				max=a[i];
				b[i]=max-min;
			}
			if(b[i]>gap) gap=b[i];
		}
		if(gap) printf("%d\n", gap);
		else printf("UNFIT\n");
	}
	return 0;
}

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Mwo2CjMgNyAxIDQgMiA0CjUKNSA0IDMgMiAxCjUKNCAzIDIgMiAz

3
6
3 7 1 4 2 4
5
5 4 3 2 1
5
4 3 2 2 3