#include <bits/stdc++.h>
using namespace std;
#define rep(i,s,e) for (int i = s; i <= e; ++i)
#define rrep(i,s,e) for (int i = s; i >= e; --i)
#define pb push_back
#define pf push_front
#define fi first
#define se second
#define all(a) a.begin(), a.end()
typedef long long ll;
typedef pair<int, int> ii;
typedef vector<ii> vii;
typedef vector<int> vi;
typedef vector<double> vd;
typedef vector<string> vs;
typedef vector<ll> vll;
int main() {
ios::sync_with_stdio(0);
cin.tie(0);
int n, m; cin >>n >> m;
vector<ii> v[2*n];
set<ii> st;
set<pair<ii,int>> s;
rep (i,0,m-1) {
int a, b; cin >> a >> b;
a--, b--;
if (b<a || a==0) {
s.insert({{b,a},i});
}
else {
v[a].pb({b,i});
}
}
if (s.size()<2) {
cout << "impossible\n";
return 0;
}
int l = (*s.begin()).fi.fi, x = (*s.begin()).fi.se-1, idl = (*s.begin()).se;
if (x==-1) x = n-1;
s.erase(s.begin());
int r = (*s.begin()).fi.fi, y = (*s.begin()).fi.se-1, idr = (*s.begin()).se;
if (y==-1) y = n-1;
s.erase(s.begin());
if (y<x) {
swap (l, r);
swap (y, x);
swap (idl, idr);
}
bool suc = 1, ans[m+1] = {};
ans[idr] = 1;
for (auto sth : s) {
st.insert({sth.fi.fi, sth.se});
}
rep (i,0,n-1) {
for (ii bi : v[i]) st.insert(bi);
if (i>l && i<=x) {
if (st.size()>1 && (*prev(st.end(),2)).fi>=i) {
l = (*prev(st.end(),2)).fi;
st.erase(prev(st.end(),2));
}
else if (st.size() && (*prev(st.end())).fi>=i) {
l = (*prev(st.end())).fi;
st.erase(prev(st.end()));
}
else {
suc = 0;
break;
}
}
if (i>r && i<=y) {
if (st.size() && (*st.rbegin()).fi>=i) {
ans[(*st.rbegin()).se] = 1;
r = (*st.rbegin()).fi;
st.erase(--st.end());
}
else {
suc = 0;
break;
}
}
}
if (!suc) {
cout << "impossible\n";
}
else {
rep (i,0,m-1) cout << ans[i];
cout << "\n";
}
return 0;
}
