#include <bits/stdc++.h>
using namespace std;

//type
#define ll long long
typedef pair<int, int> P;
//定数
#define INF 1000000000000 //10^12:∞
#define MOD 1000000007    //10^9+7:合同式の法
#define MAXR 100000       //10^5:配列の最大のrange
//略記
#define PB push_back //挿入
#define MP make_pair //pairのコンストラクタ
#define F first      //pairの一つ目の要素
#define S second     //pairの二つ目の要素
#define Z class
// OTHER
// xの二乗を返す (関数テンプレート版)
template <typename T>
T square(T x) { return x * x; }
#define chmax(x, y) (x = max(x, y))
#define chmin(x, y) (x = min(x, y))
// loop
#define rep(i, n) for (int i = 0; i < (n); i++)
#define REPD(i, n) for (ll i = n - 1; i >= 0; i--)
#define FOR(i, a, b) for (ll i = a; i <= ll(b); i++)
#define FORD(i, a, b) for (ll i = a; i >= ll(b); i--)
#define FORA(i, I) for (const auto &i : I)

// vector
#define ALL(x) x.begin(), x.end()

// output
#define YES() printf("YES\n")
#define NO() printf("NO\n")
#define isYES(x) printf("%s\n", (x) ? "YES" : "NO")
#define Yes() printf("Yes\n")
#define No() printf("No\n")
#define ln cout << '\n'
template <Z A>
void pr(A a)
{
  cout << a;
  ln;
}
template <Z A, Z B>
void pr(A a, B b)
{
  cout << a << ' ';
}

int ans = 0;
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *

int main()
{
  string a, b, c, n, x, y;
  cin >> a >> b >> c;
  // cin >> a >> b >> c;
  if ((a[a.length() - 1] == b[0]) && (b[b.length() - 1] == c[0]))
    YES();
  else
    NO();
  return 0;
}
#include<stdio.h>
 
int main(){
  char a[100];
  scanf("%[^\n]", a);
	int ctr = 0;
	
  for(int i= 0; a[i] != '\0'; i++){
    if(a[i] == ' '){
		if(a[i - 1] == a[i + 1]){
			ctr++;
		}
    }
  }
  if(ctr == 2){
  	printf("YES\n");
  }
  else{
  	printf("NO\n");
  }
  return 0;
}