const fi='daytangdan.inp'; fo='daytangdan.out'; type mang = array [1..100000] of longint; var a:mang; i,j,n:longint; function check(a: mang):boolean; begin for i:=1 to n-1 do for j:=i+1 to n do if a[i]>a[j] then exit(false); exit(true); end; begin assign(input,fi); reset(input); readln(n); for i:=1 to n do read(a[i]); close(input); assign(output,fo); rewrite(output); if check(a) then write('YES') else write('NO'); close(output); end.
