#include<bits/stdc++.h>
using namespace std;
long long N,K,ans;
long long days[1000005];
int main(){
    freopen("kanmoo.in","r",stdin);
    freopen("kanmoo.out","w",stdout);
    cin>>N>>K;
    for(int i=0;i<N;i++)
    {
        cin>>days[i];
        if(i==0)
         ans+=K+1;
        else{
            long long ext=days[i]-days[i-1];
            long long startcost=K+1;
            ans+=min(ext,startcost);
        }
    }
    cout<<ans;
    return 0;
}