#include <iostream>
using namespace std;
 
void solve() {
    string s, t;
    cin>>s>>t;
 
    /*
     * len stores the length of the prefix of S already found.
     * pos stores the current index in T.
     */
    int len = 0, pos=0;
    while(len<s.length() && pos<t.length()) {
 
        /* if the letter at position len matches. */ 
        if(s[len]==t[pos]) {
            len++;
        }
 
        pos++;
    }
 
    cout<<len<<endl;
}
int main() {
	solve();
	return 0;
}

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