#include <bits/stdc++.h>
using namespace std;
int n, m;
bool arr[109];
int memo[109][109];
int solve(int day, int cup) {
if (day >= n) return 0;
int &ret = memo[day][cup];
if (ret != -1) return ret;
ret = 1e9 + 9;
if (arr[day] == 1) {
ret = min(ret, solve(day + 1, cup));
}
ret = min(ret, solve(day + 1, cup) + 10000);
ret = min(ret, solve(day + 3, cup + 1) + 25000);
ret = min(ret, solve(day + 5, cup + 2) + 37000);
if (cup >= 3) {
ret = min(ret, solve(day + 1, cup - 3));
}
return ret;
}
int main() {
ios::sync_with_stdio(0);
cin.tie(0); cout.tie(0);
cin >> n >> m;
for (int i = 0; i < m; i++) {
int num; cin >> num;
arr[--num] = true;
}
fill(&memo[0][0], &memo[108][109], -1);
cout << solve(0, 0) << '\n';
}
