n=int(input())
l=[int(x) for x in input().split()]
l.sort()
count=1
for i in range(0,len(l)):
if(l[i]>=count):
count+=1
print(count-1)#include <bits/stdc++.h>
using namespace std;
int main()
{
#ifndef ONLINE_JUDGE
freopen("input.text", "r", stdin);
freopen("outputs.text", "w", stdout);
#endif
int n;
cin>>n;
vector<int> v;
for(int i=0; i<n; i++){
int x;
cin>>x;
v.push_back(x);
}
sort(v.begin(), v.end());
int day=0;
for(int i=0; i<n; i++){
if(v[i]>day){
day++;
}
else{
continue;
}
}
cout<<day<<endl;
return 0;
}
1350A - Orac and Factors | 1373A - Donut Shops |
26A - Almost Prime | 1656E - Equal Tree Sums |
1656B - Subtract Operation | 1656A - Good Pairs |
1367A - Short Substrings | 87A - Trains |
664A - Complicated GCD | 1635D - Infinite Set |
1462A - Favorite Sequence | 1445B - Elimination |
1656C - Make Equal With Mod | 567A - Lineland Mail |
1553A - Digits Sum | 1359B - New Theatre Square |
766A - Mahmoud and Longest Uncommon Subsequence | 701B - Cells Not Under Attack |
702A - Maximum Increase | 1656D - K-good |
1426A - Floor Number | 876A - Trip For Meal |
1326B - Maximums | 1635C - Differential Sorting |
961A - Tetris | 1635B - Avoid Local Maximums |
20A - BerOS file system | 1637A - Sorting Parts |
509A - Maximum in Table | 1647C - Madoka and Childish Pranks |