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: Runtime Error)

#include <stdio.h>

int main(int argc, const char * argv[]) {
    int x, tmpx;
    int i;
    
    scanf("%d", &x);
    while(x-->0) {
        tmpx = x;
        for(i=tmpx-1; i>0; i--) {
            while(tmpx%i==0) {
                tmpx /= i;
                if(tmpx==1) {
                    printf("%d", x);
                    return 1;
                }
            }
        }
    }
    return 0;
}