#include <stdio.h>
#include <stdlib.h>

int p,l,r,mid,prod,nr,rez,sol;
int main(){

    freopen( "fact.in" , "r" , stdin );
    freopen( "fact.out" , "w" , stdout );

    scanf( "%d" , &p );
    l=1;
    r=500000000;

    while( l <= r ){
        mid =( l + r )/2;
        prod = 5;
        nr = 0;
        while( mid/prod > 0 ){
            nr += mid/prod;
            prod = prod * 5;
        }
        if( nr < p ){
            l = mid + 1;
        }else{
            r = mid - 1;
            rez = nr;
            sol = mid;
        }
    }

    if( rez == p ){
       printf( "%d" , sol );
    }else{
        printf("-1");
    }

  return 0;
}