#include <stdio.h>
#include <stdlib.h>

#define ENDD '\0'
#define KIGY '\n'

#define TRUE 0
#define FALSE 1

int main()
{
        int ch;
        char buff[100000+1];
        int buffi;
        int N;
        int jen[100000+1];

        buffi = 0;
        while( (ch=getc(stdin)) != KIGY) {
                buff[buffi++] = ch;
        }
        buff[buffi] = ENDD;
        N = atoi(buff);


        buffi=0;
        int count = 1;
        while( (ch=getc(stdin)) != EOF) {
                        if( ch==' ' ||  ch==KIGY   ) {
                                buff[buffi] = ENDD;
                                jen[atoi(buff)] = count++;
                                buffi = 0;
                        }
                        else {
                                buff[buffi++] = ch;
                        }
        }

        count = 0;
        for( int i = N; i >=2; i-- ) {
                if( jen[i] > jen[i-1] ) {
                        continue;
                }

                count++;
                jen[i-1] = 1;
                for( int j = 1; j <= i-2; j++ ) {
                        jen[j]--;
                }
        }

        /* search max */
        printf("%d\n", count );

        return 0;
}