"简简单单"

要用long long!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

#include<bits/stdc++.h>
using namespace std;
int main(){
    long long n,a[1005]={};
    cin>>n;
    for(int i=1;i<=n;i++) cin>>a[i];
    long long sum=a[1];
    for(int i=2;i<=n;i++){
        if(a[i]>a[i-1]) sum+=a[i];
        else sum+=a[i-1]+1,a[i]=a[i-1]+1;
    }
    cout<<sum;
    return 0;
}