PAT-B1060

#include<stdio.h>
int day[1000010]={0}, day1[1000010]={0};
int main(){
int i, n, max=0, temp, pre=1000005,  sum=0, result=0;
scanf("%d",&n);
for(i=0;i<n;i++){
	scanf("%d",&temp);
	day[temp]++;
	if(temp>max)max=temp;
}
//for(i=0;i<=max;i++)printf("%d:%d ",i,day[i]);printf("\n");
for(i=max;i>=0;i--){
	day1[i]=sum;
	sum=sum+day[i];
}
//for(i=0;i<=max;i++)printf("%d:%d ",i,day1[i]);printf("\n");
for(i=max;i>=0;i--){
	if(day1[i]>=i){result=i;break;}
}
printf("%d",result);
return 0;
}