//
// Created by trudbot on 2022/6/23.
//
#include <bits/stdc++.h>
using namespace std;
int arr[201];
int main() {
int n, N;
cin >> n >> N;
for(int i=1; i<=n; i++){
cin >> arr[i];
}
int sum = 0;
int min = N;
for(int i=n; i>=0; i--){
if(arr[i] < min){
sum += (min - arr[i]) * i;
min = arr[i];
}
}
cout << sum << endl;
return 0;
}