import math
import bisect
import itertools
import sys
I=lambda : sys.stdin.readline()
mod=10**9 +7
'''fact=[1]*100001
ifact=[1]*100001
for i in range(1,100001):
    fact[i]=((fact[i-1])*i)%mod
    ifact[i]=((ifact[i-1])*pow(i,mod-2,mod))%mod
def ncr(n,r):
    return (((fact[n]*ifact[n-r])%mod)*ifact[r])%mod
def npr(n,r):
    return (((fact[n]*ifact[n-r])%mod))
    '''

def modu(a,m):
    if a%m:
        return a%m
    return m

def mindiff(a):
    b=a[:]
    b.sort()
    m=10000000000
    for i in range(len(b)-1):
        if b[i+1]-b[i]<m:
            m=b[i+1]-b[i]
    return m
    
def lcm(a,b):
    return a*b//math.gcd(a,b)

    
def merge(a,b):
    i=0;j=0
    c=0
    ans=[]
    while i<len(a) and j<len(b):
        if a[i]<b[j]:
            ans.append(a[i])
            i+=1
        else:
            ans.append(b[j])
            c+=len(a)-i
            j+=1
    ans+=a[i:]
    ans+=b[j:]
    return ans,c
def mergesort(a):
    if len(a)==1:
        return a,0
    mid=len(a)//2   
    left,left_inversion=mergesort(a[:mid])
    right,right_inversion=mergesort(a[mid:])
    m,c=merge(left,right)
    c+=(left_inversion+right_inversion)
    return m,c
    
def is_prime(num):
    if num == 1: return False
    if num == 2: return True
    if num == 3: return True
    if num%2 == 0: return False
    if num%3 == 0: return False
    t = 5
    a = 2
    while t <= int(math.sqrt(num)):
        if num%t == 0: return False
        t += a
        a = 6 - a
    return True
    
  
def ceil(a,b):
    if a%b==0:
        return a//b
    else:
        return (a//b + 1)


def ncr1(n,r):
    s=1
    for i in range(min(n-r,r)):
        s*=(n-i)
        s%=mod
        s*=pow(i+1,mod-2,mod)
        s%=mod
    return s


#/////////////////////////////////////////////////////////////////////////////////////////////////

n=int(input())
s=input()
for i in range(n-1):
    if s[i]>s[i+1]:
        print("YES")
        print(i+1,i+2)
        break
else:
    print("NO")
    
        