#include <bits/stdc++.h>
using namespace std;
#define rep(i, n)  for(long long i=0;i<(long long)(n);i++)
#define REP(i,k,n) for(long long i=k;i<(long long)(n);i++)
#define pb emplace_back
#define lb(v,k) (ll)(lower_bound(all(v),(k))-v.begin())
#define ub(v,k) (ll)(upper_bound(all(v),(k))-v.begin())
#define fi first
#define se second
#define pi M_PI
#define PQ(T) priority_queue<T>
#define SPQ(T) priority_queue<T,vector<T>,greater<T>>
#define dame(a) {out(a);return 0;}
#define decimal cout<<fixed<<setprecision(15);
#define all(a) a.begin(),a.end()
#define rsort(a) {sort(all(a));reverse(all(a));}
#define dupli(a) {sort(all(a));a.erase(unique(all(a)),a.end());}
#define popcnt __builtin_popcountll
typedef long long ll;
typedef pair<ll,ll> P;
typedef tuple<ll,ll,ll> PP;
typedef tuple<ll,ll,ll,ll> PPP;
using vi=vector<ll>;
using vvi=vector<vi>;
using vvvi=vector<vvi>;
using vvvvi=vector<vvvi>;
using vp=vector<P>;
using vvp=vector<vp>;
using vb=vector<bool>;
using vvb=vector<vb>;
const ll inf=1001001001001001001;
const ll INF=1001001001;
const ll mod=998244353;
const double eps=1e-10;
template<class T> bool chmin(T&a,T b){if(a>b){a=b;return true;}return false;}
template<class T> bool chmax(T&a,T b){if(a<b){a=b;return true;}return false;}
template<class T> void out(T a){cout<<a<<'\n';}
template<class T> void outp(T a){cout<<'('<<a.fi<<','<<a.se<<')'<<'\n';}
template<class T> void outvp(T v){rep(i,v.size())cout<<'('<<v[i].fi<<','<<v[i].se<<')';cout<<'\n';}
template<class T> void outvvp(T v){rep(i,v.size())outvp(v[i]);}
template<class T> void outv(T v){rep(i,v.size()){if(i)cout<<' ';cout<<v[i];}cout<<'\n';}
template<class T> void outvv(T v){rep(i,v.size())outv(v[i]);}
template<class T> void yesno(T b){if(b)out("yes");else out("no");}
template<class T> void YesNo(T b){if(b)out("Yes");else out("No");}
template<class T> void YESNO(T b){if(b)out("YES");else out("NO");}
template<class T> void outset(T s){auto itr=s.begin();while(itr!=s.end()){if(itr!=s.begin())cout<<' ';cout<<*itr;itr++;}cout<<'\n';}
void outs(ll a,ll b){if(a>=inf-10)out(b);else out(a);}

void sol(ll n,string s){
    vp v;
    rep(i,n){
        if(i==0||s[i]!=s[i-1])v.pb(i,i);
        else v.back().se++;
    }
    vp waiting,ans;
    auto del=[&](ll a,ll b){
        while(a<=b){
            ll d=2;
            if(b-a==2)d=3;
            ans.pb(a+1,d);
            b-=d;
        }
    };
    while(v.size()){
        while(v.size()&&(waiting.size()==0||(v.back().fi==v.back().se)==(waiting.back().fi==waiting.back().se))){
            waiting.pb(v.back());
            v.pop_back();
        }
        if(v.size()==0)break;
        if(waiting.back().fi==waiting.back().se){
            del(v.back().fi,v.back().se);
            v.pop_back();
            if(v.size()){
                v.back().se+=waiting.back().se-waiting.back().fi+1;
                waiting.pop_back();
            }
        }
        else{
            del(v.back().se+1,v.back().se+1+waiting.back().se-waiting.back().fi);
            waiting.pop_back();
            if(waiting.size()){
                v.back().se+=waiting.back().se-waiting.back().fi+1;
                waiting.pop_back();
            }
        }
    }
    while(v.size()){
        if(v.back().fi==v.back().se){
            out(-1);return;
        }
        del(v.back().fi,v.back().se);
        v.pop_back();
    }
    while(waiting.size()){
        if(waiting.back().fi==waiting.back().se){
            out(-1);return;
        }
        del(0,waiting.back().se-waiting.back().fi);
        waiting.pop_back();
    }
    out(ans.size());
    for(auto x:ans)cout<<x.fi<<' '<<x.se<<endl;
}
int main(){
    ll n;cin>>n;
    string s;cin>>s;
    sol(n,s);
}