func_code_string: #include <bits/stdc++.h>   using namespace std;   int32_t main() {     ios_base::sync_with_stdio(false);     cin.tie(0);     cout.tie(0);     ;     long long n;     cin >> n;     string s, t;     cin >> s >> t;     long long sa = 0, sb = 0, ta = 0, tb = 0;     for (long long i = 0; i < n; i++) {       if (s[i] ==  a )         sa++;       else         sb++;       if (t[i] ==  a )         ta++;       else         tb++;     }     if ((ta + sa) % 2 == 1 || (tb + sb) % 2 == 1) return cout << -1, 0;     vector<pair<long long, long long> > ans;     vector<long long> va, vb;     for (long long i = 0; i < n; i++) {       if (s[i] != t[i]) {         if (s[i] ==  a )           va.push_back(i);         else           vb.push_back(i);       }     }     {       for (long long i = 0;            i < (long long)va.size() && (long long)va.size() > i + 1; i += 2)         ans.push_back(make_pair(va[i], va[i + 1]));       for (long long i = 0;            i < (long long)vb.size() && (long long)vb.size() > i + 1; i += 2)         ans.push_back(make_pair(vb[i], vb[i + 1]));     }     if ((long long)va.size() % 2 == 1) {       ans.push_back(           make_pair(va[(long long)va.size() - 1], va[(long long)va.size() - 1]));       ans.push_back(           make_pair(va[(long long)va.size() - 1], vb[(long long)vb.size() - 1]));     }     cout << ans.size() <<   n ;     for (long long i = 0; i < (long long)ans.size(); i++)       cout << ans[i].first + 1 <<     << ans[i].second + 1 <<   n ;     return 0;   }   