ХЭШИ H

#include <iostream>
#include <cmath>
#include <vector>
#include <queue>
#include <algorithm>
#include <string>
#include <stack>
#include <set>
#include <map>
#define pii pair <int,int>
#define pb(x) push_back(x)
using namespace std;
using ll = long long;
using ld = long double;
using db = double;
void cv(vector <int> &v){
    for (auto x: v) cout<<x<<' ';
    cout<<"\n";
}

void cvl(vector <ll> &v){
    for (auto x: v) cout<<x<<' ';
    cout<<"\n";
}


void cvv(vector <vector <int> > &v){
    for (auto x: v) cv(x);
    cout<<"\n";
}

void cvb(vector <bool> v){
    for (bool x: v) cout<<x<<' ';
    cout<<"\n";
}

void cvs(vector <string>  v){
    for (auto a: v){
        cout<<a<<"\n";
    }
}

void cvp(vector <pii> a){
    for (auto p: a){
        cout<<p.first<<' '<<p.second<<"\n";
    }
    cout<<"\n";
}

ll p =101,mod=1e9+7;
bool sh=0;
/*
1101
1011

1100100
1001101


1110100
1001110
ОШИБКА!!!
*/
int main()
{
    ios::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    string s,t;
    cin>>s>>t;
    if (s == t){
        cout<<0;
        exit(0);
    }
    int n = s.size();
    vector <ll> powp(n, 1);
    for (int i = 1; i < n; ++i){
        powp[i] = powp[i - 1] * p % mod;
    }
    vector <ll> sf(n), tf(n);
    sf[0] = s[0] - '0' + 1;
    tf[0] = t[0] - '0' + 1;
    for (int i = 1; i < n; ++i){
        sf[i] = sf[i - 1] + ( s[i] - '0' + 1 ) * powp[i] % mod;
        sf[i] %= mod;
        tf[i] = tf[i - 1] + (t[i] - '0' + 1) * powp[i] % mod;
        tf[i] %= mod;
    }
    if (sh){
        cout<<"sf\n"; cvl(sf);
        cout<<"tf\n"; cvl(tf);
        cout<<"powp\n"; cvl(powp);
    }
    int i = -1, mxi=-1;
    if (sh){
        cout<<"i + 1 = "<<i + 1<<"\n";
        cout<<"powp[n - 1 - (i + 1)] = "<<powp[n - 1 - (i + 1)]<<"\n";
        cout<<"sf[i + 1] * powp[n - 1 - (i + 1)] % mod = "<<sf[i + 1] * powp[n - 1 - (i + 1)] % mod<<"\n";
        cout<<"T\n";
        cout<<"n - 1 - (i + 1) = "<<n - 1 - (i + 1)<<"\n";
        cout<<"tf[ n - 1 - (i + 1)] = "<<tf[ n - 1 - (i + 1)]<<"\n";

    }

    while (i+1 < n-1){
        if (i + 1 < n - 1 && sf[i + 1] * powp[n - 1 - (i + 1)] % mod == (tf[n - 1] - tf[n - 1 - (i + 2)] + mod) % mod){
            mxi=i+1;
        }
        if (sh){
            cout<<"i + 1 = "<<i + 1<<"\n";
            cout<<"powp[n - 1 - (i + 1)] = "<<powp[n - 1 - (i + 1)]<<"\n";
            cout<<"sf[i + 1] * powp[n - 1 - (i + 1)] % mod = "<<sf[i + 1] * powp[n - 1 - (i + 1)] % mod<<"\n";
            cout<<"T\n";
            cout<<"n - 1 - (i + 2) = "<<n - 1 - (i + 2)<<"\n";
            cout<<"tf[ n - 1 - (i + 2)] = "<<tf[ n - 1 - (i + 2)]<<"\n";

        }
        i++;
    }
    cout<<n-(mxi+1);
}