不知道为什么能过

#include <bits/stdc++.h>
using namespace std;
int n, m, ka[200001], ki[200001];
string s1, s2;
set<int> q[210001];
int main() {
  cin >> n >> m;
  cin >> s1 >> s2;
  int qq = 0;
  for (int i = n; i >= 1; i--) {
    if (s1[i - 1] != s2[i - 1]) qq = i;
    ki[i] = qq;
  }
  for (int i = 1; i <= m; i++) {
    int l, r;
    cin >> l >> r;
    if (ki[l] && ki[l] <= r) q[ki[l]].insert(r);
  }

  for (int i = 1; i <= n; i++) {
    int qs = i;
    for (int s : q[i]) {
      if (ki[qs] <= s) q[ki[qs]].insert(s);
      qs = s + 1;
    }
    if (q[i].size()) ka[i] = *q[i].begin();
  }
  priority_queue<int, vector<int>, greater<int>> ms;
  for (int i = 1; i <= n; i++) {
    while (ms.size() && ms.top() < i) ms.pop();

    if (ms.size() % 2) {
      if (s1[i - 1] == '1' && s2[i - 1] == '0' && ka[i]) ms.push(ka[i]);
    } else if (s1[i - 1] == '0' && s2[i - 1] == '1' && ka[i])
      ms.push(ka[i]);

    if (ms.size() % 2) swap(s1[i - 1], s2[i - 1]);
  }
  cout << s1;
}