#include <algorithm>
#include <cstdio>
int main(void) {
  int N;
  scanf("%d", &N);
  int prevA;
  int A;
  int count = 0;
  int maxCount;
  int currentDiff;
  for (int i = 0; i < N; i++) {
    scanf("%d", &A);
    int diff = A - prevA;
    if (currentDiff == diff || i <= 1) {
      count++;
    } else {
      count = 2;
    }
    // update
    prevA = A;
    currentDiff = diff;
    maxCount = std::max(maxCount, count);
  }
  printf("%d\n", maxCount);
  return 0;
}