#include #define For(i, a, b) for(int (i)=(int)(a); (i)<(int)(b); ++(i)) #define rFor(i, a, b) for(int (i)=(int)(a)-1; (i)>=(int)(b); --(i)) #define rep(i, n) For((i), 0, (n)) #define rrep(i, n) rFor((i), (n), 0) #define fi first #define se second using namespace std; typedef long long lint; typedef unsigned long long ulint; typedef pair pii; typedef pair pil; typedef pair pli; typedef pair pll; template bool chmax(T &a, const T &b){if(a bool chmin(T &a, const T &b){if(a>b){a=b; return true;} return false;} template T div_floor(T a, T b){ if(b < 0) a *= -1, b *= -1; return a>=0 ? a/b : (a+1)/b-1; } template T div_ceil(T a, T b){ if(b < 0) a *= -1, b *= -1; return a>0 ? (a-1)/b+1 : a/b; } constexpr lint mod = 1e9+7; constexpr lint INF = mod * mod; constexpr int MAX = 200010; int main(){ int a[4]; rep(i, 4) scanf("%d", &a[i]); sort(a, a+4); rep(i, 3)if(a[i+1] - a[i] != 1){ puts("No"); return 0; } puts("Yes"); }