#include<bits/stdc++.h>
#define inf 0x3f3f3f3f3f3f3f3fll
#define debug(x) cerr<<#x<<"="<<x<<endl
using namespace std;
using ll=long long;
using ld=long double;
using pli=pair<ll,int>;
using pi=pair<int,int>;
template<typename A>
using vc=vector<A>;
inline int read()
{
    int s=0,w=1;char ch;
    while((ch=getchar())>'9'||ch<'0') if(ch=='-') w=-1;
    while(ch>='0'&&ch<='9') s=s*10+ch-'0',ch=getchar();
    return s*w;
}
inline ll lread()
{
    ll s=0,w=1;char ch;
    while((ch=getchar())>'9'||ch<'0') if(ch=='-') w=-1;
    while(ch>='0'&&ch<='9') s=s*10+ch-'0',ch=getchar();
    return s*w;
}
int ma[300005];
int mi[300005];
int a[300005];
int n;
inline void solve()
{
    n=read();
    for(int i=1;i<=n;i++) a[i]=read();

    mi[1]=ma[1]=1;
    for(int i=2;i<=n;i++)
    {
        mi[i]=a[i]<a[mi[i-1]]?i:mi[i-1];
        ma[i]=a[i]>a[ma[i-1]]?i:ma[i-1];
    }

    ll ans=0;int r=n;
    while(r>1)
    {
        int p=ma[r-1];
        if(a[r]>=a[p]) ans+=a[r]-a[p],r--;
        else
        {
            for(int i=p+1;i<=r;i++) ans+=a[i]-a[p];
            for(int i=p+1;i<=r;i++) a[p]=min(a[p],a[i]);
            r=p;
        }
    }
    printf("%lld\n",ans);
}
int main()
{
    int T=read();
    while(T--) solve();
    return 0;
}