Problem:
Score : 200 points

Problem Statement

You are given a positive integer X.
Find the largest perfect power that is at most X.
Here, a perfect power is an integer that can be represented as b^p, where b is an integer not less than 1 and p is an integer not less than 2.

Constraints

1 ≤ X ≤ 1000

X is an integer.

Input

Input is given from Standard Input in the following format:

X

Output

Print the largest perfect power that is at most X.

Sample Input 1

10

Sample Output 1

9

There are four perfect powers that are at most 10: 1, 4, 8 and 9.
We should print the largest among them, 9.

Sample Input 2

1

Sample Output 2

1

Sample Input 3

999

Sample Output 3

961

Solution in C (GCC 5.4.1) (judge verdict: Accepted)

#include <stdio.h>
#include <math.h>
int main(){
	int x,tmp;
	int ans=1;
	int i,j,k;
	scanf("%d",&x);
	for(i=2;i<x;i++){
		j=2;	
		while( pow(i,j) <= x ){
				j++;
		}
		if(j>2){
			//printf("i=%d j=%d\n",i,j);
			tmp=1;
			for(k=0;k<j-1;k++){
				tmp = tmp *i;
			}
			if ( ans < tmp){
				ans = tmp;
			}
		}
	}
	printf("%d",ans);
	return 0;
}