#include <stdio.h>

void Z_algorithm(char S[], int Z[])
{
	int i, j, k, l;
	for (l = 0; S[l] != 0; l++);
	Z[0] = l;
	for (i = 1, j = 0; i < l; i++) {
		for (; i + j < l && S[i+j] == S[j]; j++);
		Z[i] = j;
		if (j == 0) continue;
		
		for (k = 1; k < j && k + Z[k] < j; k++) Z[i+k] = Z[k];
		i += k - 1;
		j -= k;
	}
}

int main()
{
	int i, N, A[300001];
	char S[1000000];
	scanf("%d", &N);
	for (i = 1; i <= N; i++) scanf("%d", &(A[i]));
	scanf("%s", S);
	for (i = 1; i < N; i++) {
		if (A[i] < A[i+1]) S[N+i-2] = '<';
		else S[N+i-2] = '>';
	}
	if (A[N] < A[1]) S[N*2-2] = '<';
	else S[N*2-2] = '>';
	for (i = 1; i < N; i++) S[N*2+i-2] = S[N+i-2];
	S[N*3-2] = 0;
	
	int Z[1000000];
	Z_algorithm(S, Z);
	for (i = 0; i < N; i++) if (Z[N+i-1] >= N - 1) break;
	if (i < N) printf("%d\n", i);
	else printf("-1\n");
	fflush(stdout);
	return 0;
}