Scanner inpu=new Scanner(System.in);
int N;
int count=0;
N=inpu.nextInt();
int array[]=new int[N];
for (int i = 0; i <N; i++) {
array[i]=inpu.nextInt();
}
for (int i = 0; i <N-1; i++) {
if(array[i]<=array[i+1]){
count++;
}
}
if(count==N-1){
System.out.print("yes");
}else{
System.out.print("No");
}
#Python 3.8
N = int(input())
A = input().split()
def ascend(lis):
index = 0
outdex = len(lis)
while index < outdex-1:
if lis[index] > lis[index+1]:
return False
index += 1
return True
if ascend(A):
print("Yes")
else:
print("No")