#include <bits/stdc++.h>
using namespace std;
#define all(x) x.begin(),x.end()
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
template<class T> inline bool chmax(T&a,T b){if(a<b){a=b;return 1;}return 0;}
template<class T> inline bool chmin(T&a,T b){if(a>b){a=b;return 1;}return 0;}
using ll = long long;

int n,ans=1;
int a[100005];

int main(){
    ios::sync_with_stdio(false); 
    cin.tie(0);

    cin >> n;
	rep(i,n) cin >> a[i];
	sort(a,a+n);
	rep(i,n-1)if(a[i+1]-a[i]==1) ans=2;
	cout << ans << endl;
}