#include <iostream>
#include <vector>
#include <array>
#include <unordered_map>
#define ll long long
#define int long long
using namespace std;
string S;
const ll M = 1e9 + 9;
unordered_map <ll, ll> mp;
ll n, a, b, c, s, base = 37, p, X[2500][2500], dp[2500][2500], nx[2500][2500];
signed main() {
cin.tie(0);
ios::sync_with_stdio(0);
cin >> n >> S >> a >> b >> c;
for (int i=0; i<n; ++i) {
s = 0, p = 1;
for (int j=i; j<n; ++j) {
(s += (S[j]-'a'+1) * p % M) %= M;
(p *= base) %= M;
X[i][j] = s;
}
}
for (int len=0; len<n; ++len) {
mp.clear();
for (int i=n-len-1; i>=0; --i) {
if (i+2*len+1 < n) {
mp[X[i+len+1][i+2*len+1]] = i+len+1;
}
if (mp.count(X[i][i+len])) nx[i][i+len] = mp[X[i][i+len]];
else nx[i][i+len] = -1;
}
for (int i=0; i+len<n; ++i) {
if (len) {
dp[i][i+len] = min(dp[i][i+len], min(dp[i][i+len-1], dp[i+1][i+len]));
}
s = 0;
int j = i;
while (true) {
int k = nx[j][j+len];
++s;
if (k == -1) break;
dp[i][k+len] = min(dp[i][k+len], dp[i][i+len] + b + (s+1) * c - (s * (len+1) * a));
j = k;
}
}
}
cout << a*n + dp[0][n-1] << '\n';
}
