### DaysGone's blog

By DaysGone, history, 4 years ago,

#### Hello Codeforces

Can u plzz tell me an effective way to convert any decimal floating point number (either double) to an p/q (rational form) where gcd(p,q) = 1 ?? And remember that we have number given up to _6 accurate places_ after decimal point.

• -5

By DaysGone, history, 4 years ago,

Hello everyone i just came over to this problem somewhere that if i have two very very large numbers (10^9) and i want to multiply under some modulo mod...

then we have snippet like this works :

ll mulmod(ll a, ll b, ll mod)
{
ll res = 0; // Initialize result
a = a % mod;
while (b > 0)
{
// If b is odd, add 'a' to result
if (b % 2 == 1)
res = (res + a) % mod;

// Multiply 'a' with 2
a = (a * 2) % mod;

// Divide b by 2
b /= 2;
}

// Return result
return res % mod;
}


But how to handle this when b is large negative number of the order (-10^9).. plzz help thanks