#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<int,int> pii;
#define SIZE(x) (int)(x).size()
#define ALL(x) (x).begin(),(x).end()
#define ff first
#define ss second
inline ll readi(){
ll x=0,f=1;char ch=getchar();
while(ch<'0'||ch>'9'){if(ch=='-')f=-1;ch=getchar();}
while(ch>='0'&&ch<='9'){x=x*10+ch-'0';ch=getchar();}
return x*f;
}
int main(){
int N=readi();
multiset<int> s;
int ans=0;
for(int i=0;i<N;i++){
int H=readi();
if(s.find(H)==s.end()){
ans++;
}
else{
s.erase(s.find(H));
}
s.insert(H-1);
}
cout<<ans<<endl;
return 0;
}
