#include typedef long long ll; using namespace std; const int INF = 1e9; const int MOD = 1e9+7; const ll LINF = 1e18; #define FOR(i,a,b) for(int i=(a);i<(b);++i) #define REP(i,n) for(int i=0;i<(n);++i) #define REPR(i,n) for(int i=n;i>=0;i--) #define ALL(v) (v.begin(),v.end()) #define COUT(x) cout<<(x)<<"\n" int main(){ int a[4]; REP(i,4){ cin >> a[i]; } sort(a,a+4); if(a[3]-a[2]==1&&a[2]-a[1]==1&&a[1]-a[0]==1)COUT("Yes"); else COUT("No"); return 0; }