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#include<queue>
#include<cstdio>
#include<cstring>
#include<iostream>
#include<algorithm>
using namespace std;
const int N=1e5+10;
int a[N],pos[N],n;
int main(){
    cin>>n;
    for(int i=1;i<=n;i++){
        scanf("%d",&a[i]);
        pos[a[i]]=i;
    }
    for(int i=n-1;i>=1;i--){
        if(pos[i]>pos[i+1]){
            printf("%d\n",i);
            break;
        }
    }
}
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