一本通1630：SuperGCD

#include <cstdio>
#include <cstring>
typedef long long LL;
const int N = 1e4 + 7, B = 1e8;
struct Int {
    char sa[N];
    LL a[N >> 2], len;
    Int() {
        memset(sa, 0, sizeof sa), memset(a, 0, sizeof a), len = 0;
    }
    void toInt() {
        int i, j, t;

        for (i = strlen(sa) - 1; i > 7; i -= 8, ++len)
            for (j = i - 7; j <= i; ++j)
                a[len] =  a[len] * 10 + sa[j] - '0';

        for (int j = 0; j <= i; ++j)
            a[len] = a[len] * 10 + sa[j] - '0';
    }
    bool operator < (const Int &Ib) {
        if (len < Ib.len)
            return true;

        if (len > Ib.len)
            return false;

        for (int i = len; ~i; --i) {
            if (a[i] < Ib.a[i])
                return true;

            if (a[i] > Ib.a[i])
                return false;
        }

        return false;
    }
    bool operator > (Int &Ib) {
        return Ib < *this;
    }
    bool operator != (Int &Ib) {
        return Ib < *this || *this < Ib;
    }
    bool isEven() {
        return not(a[0] & 1);
    }
    void operator -= (const Int &Ib) {
        for (int i = 0; i <= len; ++i)
            a[i] -= Ib.a[i], (a[i] < 0 ? (a[i] += B, --a[i + 1]) : 0);

        while (a[len] == 0 && len)
            --len;
    }
    void Div2() {
        for (LL i = len, m = 0; ~i; --i)
            m = m * B + a[i], a[i] = m >> 1, m &= 1;

        while (a[len] == 0 && len)
            --len;
    }
    void operator *= (const int &b) {
        for (int i = 0, end = len + 1; i <= end; ++i)
            a[i] *= b, a[i + 1] += a[i] > B, a[i] %= B;

        if (a[len + 1])
            ++len;
    }
    void operator *= (const Int &Ib) {
        Int Ir;

        for (int i = 0; i <= Ib.len; Ir.len = ++i)
            for (int j = 0; j <= len; ++j, ++Ir.len)
                Ir.a[Ir.len] += a[j] * Ib.a[i], Ir.a[Ir.len + 1] += Ir.a[Ir.len] / B, Ir.a[i] %= B;

        while (Ir.a[Ir.len] == 0 && Ir.len)
            --Ir.len;

        *this = Ir;
    }
    void print() {
        int i = len;
        printf("%lld", a[i]);

        for (--i; ~i; --i)
            printf("%08lld", a[i]);

        puts("");
    }
} Ia, Ib, Ir;
int main() {
    scanf("%s%s", Ia.sa, Ib.sa);
    Ia.toInt(), Ib.toInt(), Ir.a[0] = 1;

    while (Ia != Ib) {
        if (Ia.isEven() && Ib.isEven())
            Ia.Div2(), Ib.Div2(), Ir *= 2;
        else if (Ia.isEven())
            Ia.Div2();
        else if (Ib.isEven())
            Ib.Div2();
        else if (Ia > Ib)
            Ia -= Ib;
        else
            Ib -= Ia;
    }

    Ir *= Ia;
    Ir.print();
    return 0;
}