int gcd( int m, int n )
{
while ( n != 0) {
int tmp = m % n;
m = n;
n = tmp;
}
return m;
}
double probRelprime( int n )
{
int rel = 0, tot = 0;
for ( int i = 1; i <= n; i++) {
for ( int j = i +1; j <= n; j++) {
tot++;
if ( gcd( i, j ) == 1 ) {
rel++;
}
}
}
return (double) rel / tot;
}