#include <bits/stdc++.h>
#pragma GCC optimize "trapv"
using namespace std;
int gcd(int a, int b) {
  if (b == 0) return a;
  return gcd(b, a % b);
}
int spf[1];
unordered_map<int, set<int>> s;
void sieve() {
  spf[1] = 1;
  for (int i = 2; i < 1; i++) spf[i] = i;
  for (int i = 4; i < 1; i += 2) spf[i] = 2;
  for (int i = 3; i * i < 1; i++) {
    if (spf[i] == i) {
      for (int j = i * i; j < 1; j += i)
        if (spf[j] == j) spf[j] = i;
    }
  }
}
vector<int> getFactorization(int x, int i) {
  vector<int> ret;
  while (x != 1) {
    s[spf[x]].insert(i);
    ret.push_back(spf[x]);
    x = x / spf[x];
  }
  return ret;
}
bool sortbysec(const pair<int, int> &a, const pair<int, int> &b) {
  return (a.second > b.second);
}
bool sortByVal(const pair<int, double> &a, const pair<int, double> &b) {
  return (a.second < b.second);
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  string str1, str2;
  cin >> str1;
  ;
  cin >> str2;
  ;
  int c = 0, sum = 0;
  if (str1.length() > str2.length()) {
    int temp = str1.length() - str2.length(), count = 0;
    string s1 = str1.substr(temp);
    sum = sum + temp;
    for (int i = s1.length() - 1; i >= 0; i--) {
      if (s1[i] != str2[i]) {
        sum = sum + s1.length() + str2.length() - (2 * count);
        break;
      }
      count++;
    }
  } else {
    int temp = str2.length() - str1.length(), count = 0;
    string s2 = str2.substr(temp);
    sum = sum + temp;
    for (int i = s2.length() - 1; i >= 0; i--) {
      if (s2[i] != str1[i]) {
        sum = sum + s2.length() + str1.length() - (2 * count);
        break;
      }
      count++;
    }
  }
  cout << sum << "\n";
  ;
  return 0;
}
