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

long long nrZero( long long nr ) {
    long long k;

    k = 0;
    while ( nr ) {
        nr /= 5;
        k += nr;
    }

    return k;
}

long long src( int nr ) {
    long long pos, pas;
    pos = 0;
    for ( pas = 40; pas >= 0; pas -- )
        if ( nrZero( pos + ( 1LL << pas ) ) < nr )
            pos += ( 1 << pas );

    return pos + 1;
}

int main() {
    FILE *fin = fopen( "fact.in", "r" ), *fout = fopen( "fact.out", "w" );

    long long n;

    fscanf( fin, "%lld", &n );

    fprintf( fout, "%lld", src( n ) );

    fclose( fin );
    fclose( fout );

    return 0;
}