UVa 11078 Open Credit System

//#define LOCAL
#include <iostream>
#include <cstdio>
#include <cstring>
using namespace std;

int main(void)
{
#ifdef LOCAL
freopen("11078in.txt", "r", stdin);
#endif

int T;
scanf("%d", &T);
while(T--)
{
int n, MaxAi, ans = -999999, num, i;
scanf("%d", &n);
scanf("%d", &num);
MaxAi = num;
for(i = 2; i <= n; ++i)
{
scanf("%d", &num);
ans = max(ans, MaxAi - num);
MaxAi = max(MaxAi, num);
}
printf("%d\n", ans);
}
return 0;
}