#include<bits/stdc++.h>
using namespace std;
const int N=100000;
int num[N];
int solve(int fr,int to){
    if(fr>to) return 0;
    int minnum=998244353,minpos=0;
    for(int i=fr;i<=to;i++){
        if(num[i]<minnum){
           minpos=i;
           minnum=num[i];
        }
    }
    for(int i=fr;i<=to;i++){
        num[i]-=minnum;
    }
    int ans1=minnum+solve(fr,minpos-1)+solve(minpos+1,to);
    int ans2=to-fr+1;
    return min(ans1,ans2);
}
int main()
{
    int n;
    cin>>n;
    for(int i=1;i<=n;i++){
        cin>>num[i];
    }
    cout<<solve(1,n);
    return 0;
}