#include <bits/stdc++.h>
#define ent '\n'
#define int long long

using namespace std;

const int maxn = 1500 + 12;

int dp[maxn][maxn];
int n, m, k;
int a, b, c;

void solve() {
    string s;
    cin >> n >> s >> a >> b >> c;
    for(int i = 0; i <= n; i++) {
        for(int j = 0; j <= n; j++) {
            dp[i][j] = 1e18;
        }
    }
    dp[0][0] = 0;
    for(int j = 1; j <= n; j++) {
        dp[0][j] = j * a + c;
    }
    for(int i = 0; i <= n; i++) {
        for(int j = 0; j <= n; j++) {
            dp[i + 1][j] = min(dp[i + 1][j], dp[i][j] + a);
            dp[i + j][j] = min(dp[i + j][j], dp[i][j] + c);
        }
    }
    cout << *min_element(dp[n], dp[n] + n + 1) << ent;
}

int32_t main() {
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);

    int t = 1;
    // cin >> t;
    while (t--) {
        solve();
    }
}