def solve(N, S):
    values = [1 if c == '0' else -1 for c in S]
    
    prefix_sum = 0
    min_prefix_sum = 0
    max_difference = 0
    
    for val in values:
        prefix_sum += val
        max_difference = max(max_difference, prefix_sum - min_prefix_sum)
        min_prefix_sum = min(min_prefix_sum, prefix_sum)
    
    return max_difference

if __name__ == "__main__":
    N = int(input())
    S = input().strip()
    
    print(solve(N, S))