#include <cstdio>
#include <stdlib.h>
using namespace std;

FILE *in_file = fopen("fact.in", "r");
FILE *out_file = fopen("fact.out", "w");

int findTrailingZeros(int n){

    int counter = 0;
    for(int i = 5; n/i >= 1; i *= 5 )
        counter += n/i;
    return counter;
}

int binarySearch(int left, int right, unsigned int p)
{
    int mid, temp, k;
    while( left <= right )
    {
        mid = (left + right)/2;
        temp = findTrailingZeros(mid);
        if( temp == p ){
            k = mid;
            right = mid-1;
        }
        else if( temp > p )
            right = mid -1;
        else
            left = mid + 1;
    }
    return k;
}

int main()
{
    unsigned int p; // range ( 0 -> 4.000.000 )
    int ans = 0;

    fscanf(in_file, "%lu", &p);

    ans = binarySearch(1, 2100000000, p);

    fprintf(out_file, "%d", ans != 0 ? ans : -1 );

    return 0;
}