text: #define _USE_MATH_DEFINES
  #include <iostream>
  #include <cmath>
  #include <iomanip>
  #include <vector>
  #include <string>
  #include <algorithm>
  #include <unordered_set>
  #include <ctype.h>
  #include <queue>
  #include <map>
  #include <numeric>
  #include <set>
  
  typedef long long ll;
  using namespace std;
  
  
  int main()
  {
  	ll i, j, k;
  	
  	ll cases;
  	ll temp;
  	ll lastClean = 0;
  	ll cleans = 0;
  	vector<ll> pushes;
  	vector<ll> tempPushes;
  	cin >> cases;
  
  	for (i = 0; i < cases; i++)
  	{
  		cin >> temp;
  		pushes.push_back(temp);
  	}
  
  	for (i = 0; i < cases; i++)
  	{
  		temp = 0;
  		for (j = 0; j < tempPushes.size(); j++)
  		{
  			temp += pushes[i] - lastClean - tempPushes[j];
  			
  		}
  
  		if (temp < 20)
  		{
  			tempPushes.push_back(pushes[i] - lastClean);
  		}
  		else
  		{
  			lastClean = pushes[i];
  			cleans++;
  			tempPushes.clear();
  			tempPushes.push_back(pushes[i] - lastClean);
  		}
  	}
  	cout << cleans + 1 << "\n";
  	return 0;
  }
  
  
  
  