496 D

/// https://codeforces.com/contest/496/problem/D
#include<bits/stdc++.h>

#pragma GCC optimize ("O3")
#pragma GCC optimize ("Ofast")
#pragma GCC optimize ("unroll-loops")

#define y1 yy
#define I first
#define II second
#define ver1 v*2+1
#define ver2 ver1+1
#define tm ((tl+tr)>>1)
#define pb push_back
#define accelerate ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0)

#define vec2(type,row,col,name,val) vector<vector<type>> name((row), vector<type>((col), val))
#define matrix(type,name,n,m) type **name; name = new type*[(n)]; for (int i = 0; i < (n); i++) *(name + i) = new type[m];
#define pairprint(v) cout<<(v).I<<' '<<(v).II<<endl;
#define vec(type,col,name,val) vector<type> name((col), val)
#define pairrev(v) swap(v.I,v.II)
#define all(NAME) (NAME).begin(),(NAME).end()
#define rall(NAME) (NAME).rbegin(),(NAME).rend()
#define square(x) ((x) * (x))
#define dig(c) ((ll)(c)-'0')

#define left lft
#define right rght

using namespace std;

using ll = long long;
using ld = long double;
using pairll = pair<ll,ll>;
using ull = unsigned long long;

const ll DIM = 2e5+1;
const ll MOD = 998244353;
const ll LOG = 18;
const ll INF = 1e9+7;
const ld PI = 2*asin(1);

const char *type = (sizeof(ll) == sizeof(long long) ? "%lld" : sizeof(ll) == sizeof(short) ? "%hd" : "%d");

bool is_prime(ll &x){
    for (ll i=2; i*i<=x; i++) if (x%i == 0) return false;
    return true;
}

bool is_number(string &s){
    for (char c: s){
        if (c > '9' || c < '0') return false;
    }
    return true;
}

struct line{
    ll k, b, x, num;
};

struct segment{
    ll l, r, num;
};

void coutmod(ll x, ll mod = INF){
    cout << (x%mod + mod) % mod << '\n';
}

struct triple{
    ll I, II, III;
};

template<class T>
void right_shift(T &a){
    auto tmp = a.back();
    for (ll i=a.size()-1; i>-1; i--){
        a[i] = a[i-1];
    }
    a[0] = tmp;
}

struct fraction{
    ll num, denum;
    fraction(ll a, ll b){
        num = a / __gcd(a, b);
        denum = b / __gcd(a, b);
    }
    bool operator==(const fraction b){
        return (num == b.num && denum == b.denum);
    }
    bool operator<(const fraction b){
        if (*this == b) return false;
        if (b.denum == 0 && denum == 0) return (num < b.num);
        if (b.denum == 0) return true;
        if (denum == 0) return false;
        ll n1 = num, n2 = b.num, m1 = denum, m2 = b.denum;
        ll m3 = m1 * m2 / __gcd(m1, m2);
        n1 *= (m3 / m1);
        n2 *= (m3 / m2);
        return (n1 < n2);
    }

};
fraction operator*(fraction a, fraction b){
    return fraction(a.num * b.num, a.denum * b.denum);
}
fraction operator+(fraction a, fraction b){
    return fraction(a.num * b.denum + b.num * a.denum, a.denum * b.denum);
}
ostream &operator<<(ostream &out, fraction &a){
    out << "( " << a.num << " / " << a.denum << " )";
    return out;
}

ll res(vector<ll>c[], ll t, ll &s){
    ll cnt[] = {0, 0};
    ll i = 0, j = 0;
    while(i < c[0].size() && j < c[1].size()){
        ll i1 = min(i+t-1, (ll)c[0].size()), j1 = min(j+t-1, (ll)c[1].size());

        if (i1 == c[0].size()){
            if (j1 == c[1].size()){
                return -1;
            }else{
                if ((c[1].size() - j) % t == 0){
                    cnt[1] += (c[1].size() - j)/t;
                    j = c[1].size();
                    break;
                }else return -1;
            }
        }
        if (j1 == c[1].size()){
            if ((c[0].size() - i) % t == 0){
                cnt[0] += (c[0].size() - i)/t;
                i = c[0].size();
                break;
            }else return -1;
        }

        if (c[0][i1] < c[1][j1]){
            cnt[0] ++;
            i = i1 + 1;
            ll l = j, r = c[1].size(), m;
            while(l<r){
                m = (l+r) >> 1;
                if (c[1][m] > c[0][i1]) r = m;
                else l = m+1;
            }
            j = r;
        }else{
            cnt[1] ++;
            j = j1 + 1;
            ll l = i, r = c[0].size(), m;
            while(l<r){
                m = (l+r) >> 1;
                if (c[0][m] > c[1][j1]) r = m;
                else l = m+1;
            }
            i = r;
        }
    }

    if (j < c[1].size()){
        if ((c[1].size()-j)%t == 0){
            cnt[1] += (c[1].size()-j) / t;
        }else{
            return -1;
        }
    }else{
        if (i < c[0].size()){
            if ((c[0].size()-i)%t == 0){
                cnt[0] += (c[0].size()-i) / t;
            }else{
                return -1;
            }
        }
    }
    if (cnt[0] == cnt[1]){
        return -1;
    }else{
        if (cnt[0] > cnt[1]){
            s = cnt[0];
            return 0;
        }else{
            s = cnt[1];
            return 1;
        }
    }
}

void solve(){
    ll n;
    cin >> n;
    vector < ll > c[2];
    for (ll i=0; i<n; i++){
        ll x;
        cin >> x;
        c[x&1].emplace_back(i);
    }
    if (c[0].size()*2 == n){
        cout << "0\n";
        return;
    }
    ll winner = (c[0].size() > c[1].size() ? 0 : 1);
    vector < pairll > ans;
    for (ll i=1; i<=c[winner].size(); i++){
        ll s = 0;
        if (res(c, i, s) == winner){
            ans.emplace_back(s, i);
        }
    }
    cout << ans.size() << '\n';
    sort(all(ans));
    for (pairll p: ans) pairprint(p);
}

int main(){
    accelerate;
    ll t = 1;
    //cin >> t;
    while(t --){
        solve();
    }
    return 0;
}