D

#include <bits/stdc++.h>

using namespace std;

#define ll     long long
#define ff     first
#define ss     second
#define pb     push_back

int main()
{

    ll int x, y, z;
    cin>>x>>y>>z;

    string s;
    cin>>s;

    int n = s.size();

    ll int dp[n+1][2];

    dp[0][0] = 0;
    dp[0][1] = z;

    for(int i=0; i<n; i++)
    {
        if(s[i] == 'a')
        {
            dp[i+1][0] = min(dp[i][0]+x, z+x+dp[i][1]);
            dp[i+1][1] = min(dp[i][1]+min(x+2*z, y), z+x+dp[i][0]);
        }
        else
        {
            dp[i+1][1] = min(dp[i][1]+x, z+x+dp[i][0]);
            dp[i+1][0] = min(dp[i][0]+min(x+2*z, y), z+x+dp[i][1]);
        }

        dp[i+1][0] = min(dp[i+1][0], z+dp[i+1][1]);
        dp[i+1][1] = min(dp[i+1][1], z+dp[i+1][0]);
    }

    cout<<min(dp[n][1], dp[n][0])<<"\n";
}