def min_operations_to_good_string(N, S):
    a = [1 if c == '1' else -1 for c in S]
    psum = [0] * (N + 1)
    for i in range(N):
        psum[i + 1] = psum[i] + a[i]

    Z = [i + 1 for i, c in enumerate(S) if c == '0']

    def can_make_good(K):
        # 先頭からK個の0を1に変える
        flip = [0] * (N + 2)
        for idx in range(K):
            flip[Z[idx]] += 1
        # 累積和でA[i]を構築
        cnt = 0
        A = [0] * (N + 1)
        for i in range(N + 1):
            if i > 0:
                cnt += flip[i]
            A[i] = psum[i] + 2 * cnt

        min_prefix = A[0]
        for i in range(2, N + 1):
            if A[i] < min_prefix:
                return False
            if A[i - 1] < min_prefix:
                min_prefix = A[i - 1]
        return True

    left, right = 0, len(Z)
    while left < right:
        mid = (left + right) // 2
        if can_make_good(mid):
            right = mid
        else:
            left = mid + 1
    return left