【cf849ABC】

const int N=201000;
int n,a[N];
int main() {
	sf(n);
	rep(i,1,n+1)sf(a[i]);
	bool ans=1;
	if(a[1]%2==0||a[n]%2==0||n%2==0){
		ans=0;
	}
	puts(ans?"Yes":"No");
	return 0;
}

const int N=201000;
int n,y[N];
double k;
int main() {
	sf(n);
	rep(i,0,n)sf(y[i]);
	int b=-1;
	rep(i,2,n)if((ll)(y[i]-y[0])*(i-1)!=(ll)(y[i]-y[1])*i){
		b=i;break;
	}
	if(~b){
		bool ans=0,tans=1;
		rep(i,2,n)if(i!=b){
			bool t=(ll)(y[i]-y[0])*(i-1)!=(ll)(y[i]-y[1])*i;
			bool s=(ll)(y[i]-y[b])!=(ll)(y[1]-y[0])*(i-b);
			if(s && t){
				tans=0;break;
			}
		}
		ans|=tans;
		tans=1;
		rep(i,2,n)if(i!=b){
			bool t=(ll)(y[i]-y[0])*(i-b)!=(ll)(y[i]-y[b])*i;
			bool s=(ll)(y[i]-y[1])*b!=(ll)(y[b]-y[0])*(i-1);
			if(s && t){
				tans=0;break;
			}
		}
		ans|=tans;
		tans=1;
		rep(i,2,n)if(i!=b){
			bool t=(ll)(y[i]-y[1])*(i-b)!=(ll)(y[i]-y[b])*(i-1);
			bool s=(ll)(y[i]-y[0])*(b-1)!=(ll)(y[b]-y[1])*i;
			if(s && t){
				tans=0;break;
			}
		}
		ans|=tans;
		puts(ans?"Yes":"No");
	}else {
		puts("No");
	}
	return 0;
}

const int N=1000;
int pre[N];
int n;
char s[N*N];
int len;
int main() {
	rep(i,0,N)pre[i]=(i-1)*i/2;
	sf(n);
	if(n==0)puts("a");
	int j,c;
	while(n>0){
		j=lower_bound(pre, pre+N, n)-pre;
		if(pre[j]>n)--j;
		n-=pre[j];
		rep(i,0,j)s[len++]='a'+c;
		++c;
	}
	printf("%s",s);
	return 0;
}