/*
PROG : milk2
LANG : C++
*/
#include<bits/stdc++.h>
typedef long long ll;
typedef long double ld;
#define pii pair<int, int>
#define pll pair<ll, ll>
#define sync ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
#define FOR(i, a, b) for(int i = (a);i < (b);i++)
#define pb push_back
#define mp make_pair
#define mod 1000000007
#define fi first
#define se second
#define sqr(a) ((a) * (a))
#define pi 3.1415926535897932
#define read ifstream in("input.txt")
#define write ofstream out("output.txt")
#define vii vector<int>
#define mii map<int, int>

using namespace std;

int n, m, k;
int x[1005], a[1005], b[1005];
bool was[1005];

void go(int pos, int step, int A, int B){
    if (pos >= n || pos < 0 || !x[pos] || was[pos])
        return;
    was[pos] = 1;
    if (step == 4)
        a[pos] = abs(pos - A) / 4;
    else
        b[pos] = abs(pos - B) / 7;
    go(pos + step, step, A, B);
    go(pos - step, step, A, B);
}

int main()
{
    //ifstream in("moocast.in");
    //ofstream out("moocast.out");
    int A, B;
    string s;
    cin >> n >> A >> B;
    cin >> s;

    A--, B--;
    for(int i = 0;i < n;i++){
        x[i] = s[i] - '0';
        a[i] = -1;
        b[i] = -1;
    }

    go(A, 4, A, B);
    memset(was, 0, 1005);
    go(B, 7, A, B);
    int ans = mod;
    for(int i = 0;i < n;i++){
        if (x[i] == 0 || a[i] == - 1 || b[i] == - 1)
            continue;
        //cout << a[i] << " " << b[i] << " " << i << endl;
        ans = min(ans, a[i] + b[i]);
    }

    if (ans == mod)
        ans = - 1;
    cout << ans;

    return 0;
    ///dont forget about initialization array please
}