CodeForces 779A Pupils Redistribution

#include<map>
#include<set>
#include<ctime>
#include<cmath>
#include<queue>
#include<string>
#include<vector>
#include<cstdio>
#include<cstring>
#include<iostream>
#include<algorithm>
#include<functional>
using namespace std;

int a[110],b[110],n;

int main()
{
    scanf("%d",&n);
    for(int i=1;i<=n;i++)
    {
        int x; scanf("%d",&x);
        a[x]++;
    }
    for(int i=1;i<=n;i++)
    {
        int x; scanf("%d",&x);
        b[x]++;
    }

    int s1=0,s2=0;

    for(int i=1;i<=5;i++)
    {
        if(a[i]==b[i]) continue;
        if(abs(a[i]-b[i])%2)
        {
            printf("-1\n");
            return 0;
        }
        if(a[i]>b[i]) s1=s1+(a[i]-b[i])/2;
        else s2=s2+(b[i]-a[i])/2;
    }

    if(s1==s2) printf("%d\n",s1);
    else printf("-1\n");

    return 0;
}