#include <stdio.h>

int main(void) {
              // your code goes here
              int i, n, s, count=0, a[100000];
              
              scanf("%d", &n);

              for(i=0;i<n;i++) scanf("%d", a+i);
              
              for(i=n-1;i>=0;i--){
                          if(a[i]==n-count) count++;
              }
              
              printf("%d", n-count);
              
              return 0;
}