A：签到。
#include<iostream> #include<cstdio> #include<cstdlib> #include<cmath> #include<cstring> #include<algorithm> using namespace std; #define ll long long int gcd(int n,int m){return m==0?n:gcd(m,n%m);} int read() { int x=0,f=1;char c=getchar(); while (c<'0'||c>'9') {if (c=='-') f=-1;c=getchar();} while (c>='0'&&c<='9') x=(x<<1)+(x<<3)+(c^48),c=getchar(); return x*f; } int a[4]; int main() { //freopen("a.in","r",stdin); //freopen("a.out","w",stdout); for (int i=0;i<4;i++) a[i]=read(); sort(a,a+4); if (a[0]==1&&a[1]==4&&a[2]==7&&a[3]==9) cout<<"YES"; else cout<<"NO"; }