#include<stdio.h>
#include<math.h>
int main()
{
    int n, i, j, count = 0;
    scanf("%d", &n);
    for(i = n; i >= 1; i--){
        for(j = n-1; j >= sqrt(n); j--){
            if(n % j == 0) count++;
        }
        if(count == 0) {
                printf("%d\n", i);
        break;
        }
        else n = n- 1;
        count = 0;
    }
    return 0;
}