import numpy as np

def min_operations_to_make_good(s):
    n = len(s)
    
    values = np.array([1 if c == '1' else -1 for c in s])
    to_convert = []
    
    for length in range(2, min(n+1, 1000)):
        running_sums = np.zeros(n - length + 1, dtype=int)
        zero_positions = [[] for _ in range(n - length + 1)]
        
        for i in range(n - length + 1):
            window = values[i:i+length]
            zeros_mask = window == -1
            
            zero_pos = np.where(zeros_mask)[0] + i
            zero_positions[i] = list(zero_pos)
            zeros = np.sum(zeros_mask)
            ones = length - zeros
            
            if zeros >= ones and zero_positions[i]:
                to_convert.append(zero_positions[i][0])
                values[zero_positions[i][0]] = 1
                
    return len(set(to_convert))

n = int(input())
s = input().strip()
print(min_operations_to_make_good(s))