#include <iostream>
#include <vector>
#include <algorithm>
#include <atcoder/string>
#include <atcoder/modint>
using namespace std;
using u64 = unsigned long long;
#define rep(i,n) for(int i=0; i<(int)(n); i++)
using modint = atcoder::static_modint<998244353>;




int main(){
    int N; cin >> N;
    vector<int> A(N); rep(i,N) cin >> A[i];
    string S; cin >> S;

    rep(i,N-1) A.push_back(A[i]);
    string G;
    rep(i,A.size()-1){
        if(A[i] < A[i+1]) G.push_back('<');
        else G.push_back('>');
    }

    auto Q = atcoder::z_algorithm(S+G);
    vector<int> goals;
    rep(i,N) if(Q[N-1+i] >= N-1) goals.push_back(i);

    if(goals.empty()){ cout << "-1\n"; return 0; }

    cout << goals[0] << endl;

    return 0;
}




struct ios_do_not_sync{
    ios_do_not_sync(){
        std::ios::sync_with_stdio(false);
        std::cin.tie(nullptr);
    }
} ios_do_not_sync_instance;