組合數取模

#include<cstdio>
#include<iostream>
#include<algorithm>
#include<cstring>
using namespace std;
typedef long long LL;
const int MOD=1e9+7;
LL n,m;

LL quick_mod(LL a, LL b) {
    LL ans=1;
    a%=MOD;
    while(b) {
        if(b&1) {
            ans=ans*a%MOD;
            b--;
        }
        b>>= 1;
        a=a*a%MOD;
    }
    return ans;
}

LL C(LL n, LL m) {
    if(m>n) return 0;
    LL ans=1;
    for(int i=1; i<=m; i++) {
        LL a=(n+i-m)%MOD;
        LL b=i%MOD;
        ans=ans*(a*quick_mod(b,MOD-2)%MOD)%MOD;
    }
    return ans;
}

LL Lucas(LL n, LL m) {
    if(m==0) return 1;
    return C(n%MOD,m%MOD)*Lucas(n/MOD,m/MOD)%MOD;
}

int main() {
    cin>>n>>m;
    cout<<Lucas(max(n,m),min(n,m))<<endl;
    return 0;
}