#include<bits/stdc++.h>
using namespace std;
#define int long long
int n,a[20000001],f=1;
inline int que(int x,int y){
    x--;
    return (x+1)*n-(1+x)*x/2+y;
}
signed main(){
    freopen("sorttros.in","r",stdin);
    freopen("sorttros.out","w",stdout);
    cin>>n;
    for(int i=1;i<=n;i++)scanf("%d",&a[i]),f&=(a[i]==n-i+1);
    if(f){
        cout<<1ll*(n-1)*n/2;
    }else{
//        for(int k=1;k<=n*(n-1)/2;k++){
//            for(int i=1;i<=n;i++){
//                for(int j=1;j<=n-i;j++){
//                    if((a[j]>a[j+1])||k==que(i,j)){
//                        swap(a[j],a[j+1]);
//                    }  
//                }
//            }
//        }
        cout<<n;
    }
    fclose(stdin);
    fclose(stdout);
    return 0;
}