#include <stdio.h>

int main()
{
    freopen("domine.in","r",stdin);
    freopen("domine.out","w",stdout);
    int i,pada,n,h;
    scanf("%d",&n);
    i = 1; 
    pada = 1;     
    while ((pada<n) && (i<=pada))
    {
          scanf("%d",&h);
	      if ( h+i-1 > pada )	
	         pada = h+i-1;
	      i++; 
    }
    if (pada>n) pada=n;
    printf("%d\n",pada);
	return 0;
}