P5149 如题 本蒟蒻在将scanf读入n改为cin读入后就ac了，但不改一个点都过不了，求原因

#include <bits/stdc++.h>
#define MAX 100010
typedef long long int LL;
using namespace std;
int a[MAX],tmp[MAX];
string dic;
map<string,int>m;
LL merge_sort(int q[MAX],int l,int r) //归排求逆序对 
{
    if(l>=r) return 0;
    int mid=(l+r)>>1;
    LL ans=merge_sort(q,l,mid)+merge_sort(q,mid+1,r);
    int k=0,i=l,j=mid+1;
    while(i<=mid&&j<=r)
    {
        if(q[i]<=q[j]) tmp[k++]=q[i++];
        else
        {
            ans+=mid-i+1;
            tmp[k++]=q[j++];
        }
    }
    while(i<=mid) tmp[k++]=q[i++];
    while(j<=r) tmp[k++]=q[j++];
    for(i=l,j=0;i<=r;i++,j++) q[i]=tmp[j];
    return ans;
}
int main() {
    std::ios::sync_with_stdio(false);
    std::cin.tie(0);
    int n;
    string s;
    scanf("%d",&n);
    for(int i=0;i<n;i++)
    {
        cin>>dic;
        m[dic]=i;
    }
    for(int i=0;i<n;i++) 
    {
        cin>>s;
        a[m[s]]=i+1;
    }
    cout<<merge_sort(a,0,n-1);
    return 0;
}