#include <cstdio>

using namespace std;

inline int nz( int n )
{
    int k=0;
    while( n>=5 )
        k+=(n/5), n/=5;
    return k;
}

int main()
{
    //freopen( "fact.in", "r", stdin );
    //freopen( "fact.out", "w", stdout );
    int p, k=0, i;
    scanf( "%d", &p );
    for( i=(1<<30);i>=1;i/=2 )
        if( nz(k+i)<p )
            k+=i;
    if( nz(k+1)!=p )
        k=-2;
    printf( "%d", k+1 );
    return 0;
}