牛客练习赛43 B题

#include<iostream>
#include<cstdio>
#include<vector>
#define ll long long
using namespace std;
vector<int> lis;
ll pow_mod(ll a, ll b, ll mod){
    ll ans = 1;
    a %= mod;
    while(b){
        if(b&1){
            ans = ans * a %mod;
        }
        a = a * a % mod;
        b >>= 1;
    }
    return ans;
}
int main()
{
    int l;
    ll n,m,k1,k2,ys,cs;
    scanf("%d",&l);
    while(l--){
        scanf("%lld %lld %lld %lld",&m,&n,&k1,&k2);
        ll ans = (m%n)%n * pow_mod(10,k1-1,n)%n;
        for(ll i=k1;i<=k2;i++,ans = ans%n){
            ans *= 10;
            printf("%d",ans/n);
        }
        printf("\n");
    }
    return 0;
}