#include <bits/stdc++.h>
typedef long long ll;
using std::cout ;
using std::endl ;
using std::cin ;
using std::string ;
using std::vector ;
using std::set ;
using std::map ;
using std::pair ;
#define rep(i,n) for(int i=0, i##_end=(n); i<i##_end; i++)
void debug_out() { cout << endl; }
template <typename Head, typename... Tail>
void debug_out(Head H, Tail... T) {
  cout << H << " ";
  debug_out(T...);
}
template<class T>bool updateMax(T &a, const T &b) { if (a<b) { a=b; return 1; } return 0; }
template<class T>bool updateMin(T &a, const T &b) { if (b<a) { a=b; return 1; } return 0; }
#define all(c) c.begin(),c.end()
#ifdef _DEBUG
#define debug(...) debug_out(__VA_ARGS__)
#else
#define debug(...)
#endif

int main() {
    string S, T;
    cin >> S >> T;
    
    cout << ((T.size() == S.size() + 1 && std::equal(std::begin(S), std::end(S), std::begin(T))) ? "Yes" : "No") << endl;
    return 0;
}

