CodeForces 731B Coupons and Discounts

#pragma comment(linker, "/STACK:1024000000,1024000000")
#include<cstdio>
#include<cstring>
#include<cmath>
#include<algorithm>
#include<vector>
#include<map>
#include<set>
#include<queue>
#include<stack>
#include<ctime>
#include<iostream>
using namespace std;
typedef long long LL;
const double pi=acos(-1.0),eps=1e-10;
void File()
{
    freopen("D:\\in.txt","r",stdin);
    freopen("D:\\out.txt","w",stdout);
}
template <class T>
inline void read(T &x)
{
    char c = getchar();
    x = 0;
    while(!isdigit(c)) c = getchar();
    while(isdigit(c))
    {
        x = x * 10 + c - ‘0‘;
        c = getchar();
    }
}

int a[200010],n;

int main()
{
    cin>>n;
    for(int i=1;i<=n;i++) cin>>a[i];
    bool fail=0;
    for(int i=1;i<n;i++)
    {
        if(a[i]<0) fail=1;
        a[i]=a[i]%2;
        if(a[i]==1)
        {
            a[i]--;
            a[i+1]--;
        }
    }
    a[n]=a[n]%2;
    if(a[n]!=0) fail=1;

    if(fail==1) printf("NO\n");
    else printf("YES\n");

    return 0;
}