#include <bits/stdc++.h>
using namespace std;
int inf_int = 2e9;
long long inf_ll = 2e18;
const double pi = 3.1415926535898;
template <typename T, typename T1>
void prin(vector<pair<T, T1> >& a) {
  for (int i = 0; i < a.size(); i++) {
    cout << a[i].first << " " << a[i].second << "\n";
  }
}
template <typename T, typename T1>
void prin(set<pair<T, T1> >& a) {
  for (auto it = a.begin(); it != a.end(); it++) {
    cout << it->first << " " << it->second << "\n";
  }
}
template <typename T>
void prin(vector<T>& a) {
  for (int i = 0; i < a.size(); i++) {
    cout << a[i];
    if (i < a.size() - 1)
      cout << " ";
    else
      cout << "\n";
  }
}
template <typename T>
void prin(set<T>& a) {
  for (auto it = a.begin(); it != a.end(); it++) {
    cout << *it << " ";
  }
}
template <typename T>
void prin_new_line(vector<T>& a) {
  for (int i = 0; i < a.size(); i++) {
    cout << a[i] << "\n";
  }
}
template <typename T, typename T1>
void prin_new_line(vector<pair<T, T1> >& a) {
  for (int i = 0; i < a.size(); i++) {
    cout << a[i].first << " " << a[i].second << "\n";
  }
}
int sum_vec(vector<int>& a) {
  int s = 0;
  for (int i = 0; i < a.size(); i++) {
    s += a[i];
  }
  return s;
}
template <typename T>
T max(vector<T>& a) {
  T ans = a[0];
  for (int i = 1; i < a.size(); i++) {
    ans = max(ans, a[i]);
  }
  return ans;
}
template <typename T>
T min(vector<T>& a) {
  T ans = a[0];
  for (int i = 1; i < a.size(); i++) {
    ans = min(ans, a[i]);
  }
  return ans;
}
template <typename T>
T min(T a, T b, T c) {
  return min(a, min(b, c));
}
template <typename T>
T max(T a, T b, T c) {
  return max(a, max(b, c));
}
long double s_triangle(long double x1, long double y1, long double x2,
                       long double y2, long double x3, long double y3) {
  return abs(((x2 - x1) * (y3 - y1) - (x3 - x1) * (y2 - y1)) / 2);
}
bool overflow(long long a, long long b) {
  if (a * b / b != a) return true;
  return false;
}
bool debug = 0;
const int maxn = 2e5 + 200;
long long mod = 1e9 + 7;
void solve() {
  int n;
  cin >> n;
  vector<int> a;
  vector<int> b;
  a.push_back(0);
  b.push_back(0);
  for (int i = 1; i <= n; i++) {
    int x;
    cin >> x;
    if (x == 1) {
      a.push_back(i);
    } else {
      b.push_back(i);
    }
  }
  int last = n;
  while (a.size() < b.size()) {
    a.push_back(inf_int);
  }
  while (b.size() < a.size()) {
    b.push_back(inf_int);
  }
  n = a.size();
  vector<pair<int, int> > ans;
  for (int i = 1; i <= n; i++) {
    int i1 = 0, e1 = 0;
    int cnt1 = 0, cnt2 = 0;
    while (1) {
      if (a[i1] == last || b[e1] == last) {
        if (a[i1] == last) {
          if (cnt1 > cnt2) {
            ans.push_back({cnt1, i});
          }
        } else {
          if (cnt2 > cnt1) {
            ans.push_back({cnt2, i});
          }
        }
        break;
      }
      if (i1 + i >= n && e1 + i >= n) {
        break;
      } else if (i1 + i < n && e1 + i < n) {
        if (a[i1 + i] < b[e1 + i]) {
          cnt1++;
          i1 = i1 + i;
          int l = e1, r = n - 1;
          int m;
          while (l <= r) {
            m = (l + r) >> 1;
            if (b[m] < a[i1]) {
              e1 = m;
              l = m + 1;
            } else {
              r = m - 1;
            }
          }
        } else {
          cnt2++;
          e1 = e1 + i;
          int l = i1, r = n - 1;
          int m;
          while (l <= r) {
            m = (l + r) >> 1;
            if (a[m] < b[e1]) {
              i1 = m;
              l = m + 1;
            } else {
              r = m - 1;
            }
          }
        }
      } else if (i1 + i < n) {
        if (a[i1 + i] == inf_int) break;
        cnt1++;
        i1 = i1 + i;
      } else {
        if (b[e1 + i] == inf_int) break;
        cnt2++;
        e1 = e1 + i;
      }
    }
  }
  sort(ans.begin(), ans.end());
  cout << ans.size() << "\n";
  for (int i = 0; i < ans.size(); i++) {
    cout << ans[i].first << " " << ans[i].second << "\n";
  }
}
int main() {
  if (!debug) {
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
  }
  int t = 1;
  while (t--) solve();
  return 0;
}
