Unsigned Long Long Won't Go Beyond The 93th Fibonacci Number?

Here's the code I wrote for finding the n-th Fibonacci number:

unsigned long long fib(int n)
{
    unsigned long long u = 1, v = 1, t;

    for(int i=2; i<=n; i++)
    {
        t = u + v;
        u = v;
        v = t;
    }

    return v;
}

While the algorithm runs pretty quickly, the output starts to freak out when n>93. I think/know it's because of the unsigned long long's 64bit size. I'm new to C++ but are there ways of getting around this so I can get the answer of something like fib(9999)?

Thanks

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