#include <algorithm>
#include <iostream>
#include <cstring>
using namespace std;
const int N = 100000;
const int M = 100000;
const int N_ = 1 << 17;
const int INF = 0x3f3f3f3f;
char aa[N + 1], bb[M + 1];
int st0[N_ << 1], st1[N_ << 1], lz[N_], h_, n_;
void put(int i) {
swap(st0[i], st1[i]);
if (i < n_)
lz[i] ^= 1;
}
void pus(int i) {
if (lz[i]) {
int l = i << 1, r = l ^ 1;
put(l), put(r), lz[i] = 0;
}
}
void pul(int i) {
if (!lz[i]) {
int l = i << 1, r = l ^ 1;
st0[i] = st0[r] != -1 ? st0[r] : st0[l];
st1[i] = st1[r] != -1 ? st1[r] : st1[l];
}
}
void push(int i) {
for (int h = h_; h; h--)
pus(i >> h);
}
void pull(int i) {
while (i >>= 1)
pul(i);
}
void build(int n) {
h_ = 0, n_ = 1;
while (n_ <= n)
h_++, n_ <<= 1;
for (int i = 0; i < n_; i++)
st0[i + n_] = i, st1[i + n_] = -1, lz[i] = 0;
for (int i = n_ - 1; i; i--)
pul(i);
}
void update(int l, int r) {
int l_ = l += n_, r_ = r += n_;
push(l_), push(r_);
for ( ; l <= r; l >>= 1, r >>= 1) {
if (l & 1)
put(l++);
if (!(r & 1))
put(r--);
}
pull(l_), pull(r_);
}
int search0(int r) {
int l = n_; push(r += n_);
for ( ; l <= r; l >>= 1, r >>= 1)
if (!(r & 1)) {
if (st0[r] != -1)
return st0[r];
r--;
}
return -1;
}
int search1(int r) {
int l = n_; push(r += n_);
for ( ; l <= r; l >>= 1, r >>= 1)
if (!(r & 1)) {
if (st1[r] != -1)
return st1[r];
r--;
}
return -1;
}
int query(int i) {
push(i += n_);
return st0[i] == -1;
}
int transform(char *aa, int n) {
int m = 0;
build(n);
for (int i = 0; i < n; i++) {
char a = aa[i];
if (a == '1')
m++;
else if (a == '2')
update(m, m), m++;
else if (a == 'U') {
if (query(m - 1))
update(m - 1, m - 1);
m--;
} else if (a == 'L')
update(search1(m - 1), m - 1);
else
update(search0(m - 1), m - 1);
}
for (int h = 0; h < m; h++)
aa[h] = query(h);
return m;
}
int main() {
cin >> aa >> bb;
int n = strlen(aa), m = strlen(bb);
n = transform(aa, n);
m = transform(bb, m);
if (n > m)
swap(n, m), swap(aa, bb);
int ans = INF, i_ = 0;
while (i_ < n && aa[i_] == bb[i_])
i_++;
for (int d = 0, i = i_; i <= n && i < i_ + 19; i++) {
ans = min(ans, n - i + abs(d) + m - i);
if (i < n)
d = d * 2 + aa[i] - bb[i];
}
cout << ans << '\n';
return 0;
}
