#include <iostream>
#include <vector>
using namespace std ;

#define int long long
const int N = 100005 , INF = 0x3f3f3f3f3f3f3f3f ;
int n , m , a[N] , b[N] ;

void ckin ( int &x , int y ) { x = min ( x , y ) ; }

vector < int > merge ( vector < int > a , vector < int > b ) {
	int n = a .size ( ) , m = b .size ( ) ;
	vector < int > c ( n + m - 1 ) ;
	for ( int &i : c ) i = INF ;
	static int x[N] , y[N] , z[N] ;
	for ( int i = 0 ; i < 12 ; ++ i ) {
		if ( i >= n ) break ;
		for ( int j = 0 ; j < 12 ; ++ j ) {
			if ( j >= m ) break ;
			int t1 = 0 , t2 = 0 , t3 = 0 ;
			for ( int k = i ; k < n ; k += 12 ) x [ t1 ++ ] = a [ k ] ;
			for ( int k = j ; k < m ; k += 12 ) y [ t2 ++ ] = b [ k ] ;
			for ( int k = t1 - 1 ; k ; -- k ) x [ k ] -= x [ k - 1 ] ;
			for ( int k = t2 - 1 ; k ; -- k ) y [ k ] -= y [ k - 1 ] ;
			int k1 = 1 , k2 = 1 ;
			while ( k1 < t1 && k2 < t2 ) {
				if ( x [ k1 ] > y [ k1 ] ) z [ ++ t3 ] = x [ k1 ++ ] ;
				else z [ ++ t3 ] = y [ k1 ++ ] ;
			}
			while ( k1 < t1 ) z [ ++ t3 ] = x [ k1 ++ ] ;
			while ( k2 < t2 ) z [ ++ t3 ] = y [ k2 ++ ] ;
			z [ 0 ] = x [ 0 ] + y [ 0 ] ;
			for ( int k = 1 ; k <= t3 ; ++ k ) z [ k ] += z [ k - 1 ] ;
			for ( int k = 0 ; k <= t3 ; ++ k ) ckin ( c [ k * 12 + i + j ] , z [ k ] ) ;
		}
	}
	return c ;
}

vector < int > solve ( int l , int r ) {
	if ( l == r ) {
		vector < int > f ( 5 ) ;
		for ( int i = 1 ; i < 5 ; ++ i ) f [ i ] = INF ;
		f [ 0 ] = 0 , f [ a [ l ] ] = b [ l ] ;
		return f ;
	}
	int mid = ( l + r ) >> 1 ;
	return merge ( solve ( l , mid ) , solve ( mid + 1 , r ) ) ;
}

int read ( ) {
	char ch = getchar ( ) ;
	int x = 0 ;
	while ( ch < '0' || ch > '9' )
		ch = getchar ( ) ;
	while ( ch >= '0' && ch <= '9' )
		x = x * 10 + ch - 48 , ch = getchar ( ) ;
	return x ;
}

signed main ( ) {
	cin >> n >> m ;
	for ( int i = 1 ; i <= n ; ++ i ) {
		int x = read ( ) ;
		b [ i ] = ( x + 4 ) / 5 * 5 ;
		a [ i ] = b [ i ] - x ;
	}
	
	vector < int > ans = solve ( 1 , n ) ;
	int siz = ans .size ( ) , res = 0 ;
	for ( int i = 0 ; i < siz - 1 ; ++ i )
		if ( ans [ i ] <= m ) res = max ( res , i ) ;
	cout << res + m % 5 << "\n" ;
	return 0 ;
}