#include <stdio.h>
int main()
{
    int t;
    scanf("%d",&t);
    while(t--)
        {
        long int x;
        int i;
        scanf("%d",&x);
        long int a[x];
        for(i=0;i<x;i++)
        {
            scanf("%ld",&a[i]);
        }
        long int min=a[0],max=0;
        for(i=0;i<x;i++)
        {
           if(a[i]<min)
           min=a[i];
           max=max+(a[i]-min);
        }
        printf("%ld\n",max);
        }
     return 0;
 
 
}
 
 

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