#include "bits/extc++.h"
using namespace std;
template <typename T>
void dbgh(const T& t) {
cerr << t << endl;
}
template <typename T, typename... U>
void dbgh(const T& t, const U&... u) {
cerr << t << " | ";
dbgh(u...);
}
#ifdef DEBUG
#define dbg(...) \
cerr << "L" << __LINE__ << " [" << #__VA_ARGS__ << "]" \
<< ": "; \
dbgh(__VA_ARGS__)
#else
#define cerr \
if (false) \
cerr
#define dbg(...)
#endif
#define endl "\n"
#define long int64_t
#define sz(x) int((x).size())
void solve() {
int n, m;
cin >> n >> m;
array<int, 3> arr[m];
for (int i = 0; i < m; i++) {
auto& [l, r, ci] = arr[i];
cin >> l >> r;
l--;
r--;
ci = i;
if (l > r) {
r += n;
}
}
sort(arr, arr + m, [&](const auto& a, const auto& b) -> bool {
if (a[0] != b[0]) {
return a[0] < b[0];
}
return a[1] > b[1];
});
for (auto& [l, r, _] : arr) {
if (r >= n) {
r -= n;
}
}
int par[m];
pair<int, int> mx {-1, -1};
for (int i = 0; i < 2 * m; i++) {
int ci = i >= m ? i - m : i;
auto [l, r, _] = arr[ci];
if (l > r) {
r += n;
}
if (i >= m) {
l += n;
r += n;
}
if (r <= mx.first) {
par[ci] = mx.second;
} else {
par[ci] = ci;
mx = {r, ci};
}
}
for (int i = 0; i < m; i++) {
int u = i;
while (par[u] != u) {
u = par[u];
}
par[i] = u;
}
vector<int> vals;
int inds[m];
for (int i = 0; i < m; i++) {
if (par[i] == i) {
inds[i] = sz(vals);
vals.push_back(i);
}
dbg(i, arr[i][0], arr[i][1], par[i]);
}
auto covers_all = [&](const vector<pair<int, int>>& arr) -> bool {
vector<int> e[n];
for (auto& [l, r] : arr) {
e[l].push_back(r);
}
int mx = -1;
for (int i = 0; i < n; i++) {
for (auto& a : e[i]) {
mx = max(mx, a);
}
if (mx < i) {
return false;
}
}
return true;
};
auto check = [&](const vector<bool>& distr) -> void {
vector<pair<int, int>> segs[2];
auto add = [&](int i, int l, int r) -> void {
if (r >= n) {
r -= n;
}
if (l > r) {
segs[i].emplace_back(l, n - 1);
segs[i].emplace_back(0, r);
} else {
segs[i].emplace_back(l, r);
}
};
bool ans[m];
for (int i = 0; i < m; i++) {
auto& [l, r, ci] = arr[i];
if (par[i] == i) {
ans[ci] = distr[inds[i]];
} else {
ans[ci] = !distr[inds[par[i]]];
}
dbg(i, inds[par[i]], ans[ci]);
add(ans[ci], l, r);
}
if (covers_all(segs[0]) && covers_all(segs[1])) {
for (auto& a : ans) {
cout << a;
}
cout << endl;
exit(0);
}
};
int k = sz(vals);
dbg(k);
if (k % 2 == 0 || k == 1) {
vector<bool> distr(k);
for (int i = 0; i < k; i++) {
distr[i] = i & 1;
}
check(distr);
cout << "impossible" << endl;
return;
} else if (k <= 3) {
for (int i = 0; i < k; i++) {
vector<bool> distr(k);
int j = i;
bool cur = true;
while (true) {
distr[j] = cur;
cur ^= true;
j = j + 1 == k ? 0 : j + 1;
if (j == i) {
break;
}
}
check(distr);
}
cout << "impossible" << endl;
return;
}
{
vector<pair<int, int>> cur;
for (auto& [l, r, _] : arr) {
if (l > r) {
cur.emplace_back(l, n - 1);
cur.emplace_back(0, r);
} else {
cur.emplace_back(l, r);
}
}
if (!covers_all(cur)) {
cout << "impossible" << endl;
return;
}
}
auto covers = [&](const vector<pair<int, int>>& segs, int ql, int qr) -> bool {
if (!sz(segs)) {
return false;
}
vector<pair<int, int>> evts;
for (auto& [l, r] : segs) {
evts.emplace_back(l - n, 1);
evts.emplace_back(r - n + 1, -1);
evts.emplace_back(l, 1);
evts.emplace_back(r + 1, -1);
evts.emplace_back(l + n, 1);
evts.emplace_back(r + n + 1, -1);
}
sort(begin(evts), end(evts));
int prev = -1, cur = 0;
for (auto& [ind, x] : evts) {
if (prev != -1 && ind != prev) {
if (!cur) {
if (ql <= ind - 1 && ind - 1 <= qr) {
return false;
} else if (ql <= prev && prev <= qr) {
return false;
}
}
}
cur += x;
prev = ind;
}
return true;
};
bool can[k];
vector<pair<int, int>> child[k];
for (int i = 0; i < m; i++) {
auto& [l, r, _] = arr[i];
if (l > r) {
r += n;
}
if (par[i] != i) {
child[inds[par[i]]].emplace_back(l, r);
}
}
array<int, 2> carr[k];
for (int i = 0; i < k; i++) {
carr[i] = {arr[vals[i]][0], arr[vals[i]][1]};
}
for (int i = 0; i < k; i++) {
int a = (i + k - 1) % k, b = (i + 1) % k;
vector<pair<int, int>> cur = child[i];
cur.emplace_back(carr[a][0], carr[a][1]);
cur.emplace_back(carr[b][0], carr[b][1]);
can[i] = covers(cur, carr[i][0], carr[i][1]);
dbg(i, can[i], carr[a][0], carr[a][1], carr[b][0], carr[b][1], carr[i][0], carr[i][1]);
}
int cnt = 0;
for (auto& a : can) {
cnt += a;
}
for (int i = 0; i < k; i++) {
int a = i, b = (i + 1) % k, c = (i + 2) % k, d = (i + 3) % k;
int ccnt = cnt - can[b] - can[c];
if (ccnt != k - 2) {
continue;
}
vector<pair<int, int>> cur;
cur.insert(cur.end(), begin(child[b]), end(child[b]));
cur.insert(cur.end(), begin(child[c]), end(child[c]));
cur.emplace_back(carr[a][0], carr[a][1]);
cur.emplace_back(carr[d][0], carr[d][1]);
if (!covers(cur, carr[b][0], carr[c][1])) {
continue;
}
dbg(i, carr[b][0], carr[c][1]);
vector<bool> distr(k);
bool cb = true;
while (true) {
distr[c] = cb;
cb ^= true;
if (c == b) {
break;
}
c = c + 1 == k ? 0 : c + 1;
}
check(distr);
// assert(false);
}
cout << "impossible" << endl;
}
int main() {
cin.tie(nullptr);
ios_base::sync_with_stdio(false);
cin.exceptions(ios::failbit);
solve();
}
