#include <bits/stdc++.h>
using namespace std;
template <typename T>
void get_int(T &x) {
  char t = getchar();
  bool neg = false;
  x = 0;
  for (; (t > '9' || t < '0') && t != '-'; t = getchar())
    ;
  if (t == '-') neg = true, t = getchar();
  for (; t <= '9' && t >= '0'; t = getchar()) x = x * 10 + t - '0';
  if (neg) x = -x;
}
template <typename T>
void print_int(T x) {
  if (x < 0) putchar('-'), x = -x;
  short a[20] = {}, sz = 0;
  while (x > 0) a[sz++] = x % 10, x /= 10;
  if (sz == 0) putchar('0');
  for (int i = sz - 1; i >= 0; i--) putchar('0' + a[i]);
}
const int inf = 0x3f3f3f3f;
const long long Linf = 1ll << 62;
const double pi = acos(-1.0);
map<int, int> ind;
char s[100111];
int n;
int main() {
  get_int(n);
  scanf("%s", s + 1);
  int len = 0, sum = 0;
  ind[0] = 0;
  for (int i = 1; i <= n; i++) {
    if (s[i] == '1')
      sum++;
    else
      sum--;
    if (ind.find(sum) == ind.end())
      ind[sum] = i;
    else
      len = max(len, i - ind[sum]);
  }
  print_int(len), puts("");
  return 0;
}
