#include
using namespace std;
int main()
{
int n;
cin>>n;
int a;
int count;
int arr[100]={0};
//input in array
if(n<1000 && n>0)
{
for(int i=0;i<n;i++)
{
cin>>a;
if(a>0 && a<1000000000)
{
arr[i]=a;
}
}
//check if first increase or decrease
if(arr[1]>arr[0]) // increasing order
{
count=1;
for(int i=1;i<n;i++)
{
if(arr[i+1]>arr[i])
{
count++;
}
}
if(count==n-1)
{
cout<<"true";
}
else
{
cout<<"false";
}
}
else /// decreasing order
{
count=1;
for(int i=2;i<n;i++)
{ if(arr[i+1]<arr[i])
{
count=count+1;
}
}
if(count==n-1)
{
cout<<"true";
}
// IF WHOLE NOT DECREASING MEANS ---> IN BETWEEN ABLE TO SPLIT-->NOW INCREASING PART
else
{
if(arr[count+1]<arr[count+2])
{
count++;
for(int i=count;i<n;i++)
{
if(arr[i+1]<arr[i])
{
break;
}
count++;
}
if(count==n-1)
{
cout<<"true";
}
else
{
cout<<"false";
}
}
else
{
cout<<"false";
}
}
}
}
return 0;
}