1005B. Delete from the Left.cpp

#include <algorithm>
#include <cmath>
#include <cstring>
#include <iostream>
#include <map>
#include <set>
#include <string>
#include <vector>
using namespace std;

using ll = long long;
using str = string;

using pii = pair<int, int>;
using pll = pair<ll, ll>;
#define mp make_pair
#define f first
#define s second

using vi = vector<int>;
using vl = vector<ll>;
using vs = vector<str>;
using vc = vector<char>;

#define sz(x) int((x).size())
#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
#define pb push_back
#define eb emplace_back

const int mod = 998244353; // 1e9+7;

void solve() {
    str s, t;
    cin >> s >> t;

    int cnt = 0;
    for (int i = sz(s) - 1, j = sz(t) - 1; i >= 0 && j >= 0; i--, j--) {
        if (s[i] == t[j]) cnt++;
        else break;
    }

    cout << (sz(s) - cnt) + (sz(t) - cnt) << '\n';
}

int main () {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);

    int tc = 1;
    // cin >> tc;

    while (tc--) solve();

    return 0;
}