#include <iostream>
#include <vector>

int current_draw_sum(const std::vector<int>& rounds_subarray, const size_t start, const size_t end) {

    int sum = 0;

    for (size_t i = start; i < end; ++i) {

        sum += rounds_subarray[i];

    }

    return sum;

}

void sum_add_element(int& sum,  const int element) {

    if (element > 0) {

        ++sum;

    } else {

        --sum;

    }

}

void sum_sub_element(int& sum,  const int element) {

    if (element > 0) {

        --sum;

    } else {

        ++sum;

    }

}

int main() {

   size_t number_of_rounds;

   std::cin >> number_of_rounds;

   std::vector<int> rounds(number_of_rounds);

   for (int& round : rounds) {

      std::cin >> round;

       if (round == 0) {
           round = -1;
       }


   }

   int prev_sum = current_draw_sum(rounds, 0, rounds.size());

   if (prev_sum == 0) {

       std::cout << rounds.size();
       return 0;

   }

   for (size_t len = rounds.size() - 1; len > 1; --len) {

       bool first_loop = true;

       //Проход окном в прямом направлении
       for (size_t pos = 0; pos + len <= rounds.size(); ++pos) {

           if (first_loop) {

               first_loop = false;
               sum_sub_element(prev_sum, rounds[pos + len]);

           } else {

               sum_sub_element(prev_sum, rounds[pos - 1]);
               sum_add_element(prev_sum, rounds[pos + len - 1]);

           }

            if (prev_sum == 0) {

                std::cout << len << std::endl;
                return 0;

            }

       }
       //Теперь в обратном но с len меншим на еденицу
       --len;

       if (len == 1) {

           break;

       }

       first_loop = true;

       for (size_t pos = rounds.size() - len; pos >= 0 && pos != std::numeric_limits<size_t>::max(); --pos) {

           if (first_loop) {

               first_loop = false;
               sum_sub_element(prev_sum, rounds[pos - 1]);


           } else {

               sum_add_element(prev_sum, rounds[pos]);
               sum_sub_element(prev_sum, rounds[pos + len]);

           }

           if (prev_sum == 0) {

               std::cout << len << std::endl;
               return 0;

           }

       }

   }

   std::cout << 0;

   return 0;
}