#include #pragma GCC optimize("Ofast") #define _GLIBCXX_DEBUG using namespace std; using std::cout; using std::cin; using std::endl; using ll=long long; using ld=long double; ll ILL=2167167167167167167; const int INF=2100000000; const ll mod=1e9+7; #define rep(i,a) for (ll i=0;i using _pq = priority_queue, greater>; template ll LB(vector &v,T a){return lower_bound(v.begin(),v.end(),a)-v.begin();} template ll UB(vector &v,T a){return upper_bound(v.begin(),v.end(),a)-v.begin();} template bool chmin(T &a,const T &b){if(a>b){a=b;return 1;}else return 0;} template bool chmax(T &a,const T &b){if(a void So(vector &v) {sort(v.begin(),v.end());} template void Sore(vector &v) {sort(v.begin(),v.end(),[](T x,T y){return x>y;});} void yneos(bool a){if(a) cout<<"Yes\n"; else cout<<"No\n";} template void vec_out(vector &p){for(int i=0;i<(int)(p.size());i++){if(i) cout<<" ";cout<>t; rep(i,t) solve(); } void solve(){ int N; cin>>N; string S,T; cin>>S>>T; auto f=[&](string U)->vector{ vector p(N-1); rep(i,N-1){ if(U[i]==U[i+1]) p[i]=1; } vector ans; rep(i,N-1){ if((i+p[i])%2) ans.push_back(i); } return ans; }; auto A=f(S),B=f(T); if(A.size()!=B.size()) cout<<"-1\n"; else{ if(N==2){ if(!A.empty()){ if(S!=T){ cout<<"-1\n"; return ; } } } ll v=0; rep(i,(int)(A.size())) v+=abs(A[i]-B[i]); cout<