#include <bits/stdc++.h>
#define REP(i, a, b) for(int i = a; i<b; i++)
#define all(v) v.begin(), v.end()
#define i64 long long
using namespace std;
int n=100000;
vector<int> aa(n, 0);
vector<int> ca(n, 0);
vector<int> ta(n, 0);
vector<int> ab(n, 0);
vector<int> cb(n, 0);
vector<int> tb(n, 0);
void init(string a, string b){
if(a[0] == 'A') aa[0] = 1;
else if(a[0] == 'C') ca[0] = 1;
else if(a[0] == 'T') ta[0] = 1;
if(b[0] == 'A') ab[0] = 1;
else if(b[0] == 'C') cb[0] = 1;
else if(b[0] == 'T') tb[0] = 1;
REP(i, 1, n){
if(a[i] == 'A') aa[i] += aa[i-1] + 1;
else aa[i] = aa[i-1];
if(a[i] == 'C') ca[i] += ca[i-1] + 1;
else ca[i] = ca[i-1];
if(a[i] == 'T') ta[i] += ta[i-1] + 1;
else ta[i] = ta[i-1];
if(b[i] == 'A') ab[i] += ab[i-1] + 1;
else ab[i] = ab[i-1];
if(b[i] == 'C') cb[i] += cb[i-1] + 1;
else cb[i] = cb[i-1];
if(b[i] == 'T') tb[i] += tb[i-1] + 1;
else tb[i] = tb[i-1];
}
// REP(i, 0, n) cerr<<ta[i]<<" ";
// cerr<<'\n';
// REP(i, 0, n) cerr<<tb[i]<<" ";
// cerr<<'\n';
// REP(i, 0, n) cerr<<ca[i]<<" ";
// cerr<<'\n';
// REP(i, 0, n) cerr<<cb[i]<<" ";
// cerr<<'\n';
// REP(i, 0, n) cerr<<aa[i]<<" ";
// cerr<<'\n';
// REP(i, 0, n) cerr<<ab[i]<<" ";
// cerr<<'\n';
}
int get_distance(int x, int y){
if(x != 0){
// cerr<<"ta[y] - tb[y] "<<ta[y] - tb[y]<<'\n';
// cerr<<"ta[x-1] - tb[x-1] "<<ta[x-1] - tb[x-1]<<'\n';
// cerr<<"aa[y] - ab[y] "<<aa[y] - ab[y]<<'\n';
// cerr<<"aa[x-1] - ab[x-1] "<<aa[x-1] - ab[x-1]<<'\n';
// cerr<<"ca[y] - cb[y] "<<ca[y] - cb[y]<<'\n';
// cerr<<"ca[x-1] - cb[x-1] "<<ca[x-1] - cb[x-1]<<'\n';
if((abs(ta[y] - tb[y]) == abs(ta[x-1] - tb[x-1])) && (abs(aa[y] - ab[y]) == abs(aa[x-1] - ab[x-1])) && (abs(ca[y] - cb[y]) == abs(ca[x-1] - cb[x-1]))){
int cnt = 0;
REP(i, x, y){
if(ta[i]-ta[x-(i+1)] != tb[i]-tb[x-(i+1)]) cnt++;
//else cnt--;
if(ca[i]-ca[x-(i+1)] != cb[i]-cb[x-(i+1)]) cnt++;
//else cnt--;
if(aa[i]-aa[x-(i+1)] != ab[i]-ab[x-(i+1)]) cnt++;
//else cnt--;
}
// cerr<<cnt<<'\n';
// int ans;
// if(cnt%2 == 0 && cnt != 0) ans = cnt/2;
// else if(cnt != 0) ans = (cnt+1)/2;
// else ans = 1;
// return ans;
int ans = y-x;
//if(ans == 1) ans = 2;
return ans;
} else{
//cerr<<12344444<<'\n';
return -1;
}
} else if(x==0){
if((abs(ta[y]) == abs(tb[y] )) && (abs(aa[y] ) == abs(ab[y])) && (abs(ca[y])== abs(cb[y]))){
int cnt = 0;
if(ta[0] != tb[0]) cnt++;
if(ca[0] != cb[0]) cnt++;
if(aa[0] != ab[0]) cnt++;
REP(i, x+1, y){
if(ta[i]-ta[x-(i+1)] != tb[i]-tb[x-(i+1)]) cnt++;
//else cnt--;
if(ca[i]-ca[x-(i+1)] != cb[i]-cb[x-(i+1)]) cnt++;
// else cnt--;
if(aa[i]-aa[x-(i+1)] != ab[i]-ab[x-(i+1)]) cnt++;
// else cnt--;
}
//cerr<<cnt<<'\n';
int ans = y-x;
//if(ans == 1) ans = 2;
return ans/2;
} else{
//cerr<<12344444<<'\n';
return -1;
}
}
return -1;
}
void solve(){
int q; cin>>n>>q;
string a, b; cin>>a>>b;
init(a, b);
while(q--){
int x, y; cin>>x>>y;
cout<<get_distance(x, y)<<'\n';
}
}
int main(){
int t=1; //cin>>t;
while(t--) solve();
}
