TLE on #25

#include<iostream>
using namespace std;
int a[2001];
int main()
{
    int n,d,s=0;
    cin>>n>>d>>a[1];
    for(int i=2;i<=n;i++)
    {
        cin>>a[i];
        while(a[i]<=a[i-1])a[i]+=d,s++;
    }
    cout<<s;
    return 0;
}