#pragma GCC optimize("Ofast")
#include<unistd.h>
inline char RC(){static char buf[65536],*p=buf,*q=buf;return p==q&&(q=(p=buf)+read(0,buf,65536))==buf?-1:*p++;}
inline void W(int n){char OB[12],OP=0,buf[12],p;if(n<0)n=-n,OB[OP++]='-';if(n==0)OB[OP++]='0';p=0;while(n)buf[p++]='0'+(n%10),n/=10;for(--p;p>=0;--p)OB[OP++]=buf[p];write(1,OB,OP);}

const int N = 3000000 + 225;
int a[N], b[N];
int occ[N], to[N];
bool vis[N];

int main(){
    int lena = 1, lenb = 1;
    char c; int eek = 0;
    while(true){
        c = RC();
        if(c == '\n'){
            a[lena] = eek;
            break;
        }
        if(c == ' '){
            a[lena++] = eek, eek = 0;
        }
        if(c >= '0'){
            eek = eek * 10 + c - '0';
        }
    }
    eek = 0;
    while(true){
        c = RC();
        if(c == '\n'){
            b[lenb] = eek;
            break;
        }
        if(c == ' '){
            b[lenb++] = eek, eek = 0;
        }
        if(c >= '0'){
            eek = eek * 10 + c - '0';
        }
    }
    if(lena != lenb){
        W(-1);
        return 0;
    }

    for(int i = 1; i <= lena; ++i){
        occ[a[i]] = i;
    }
    for(int i = 1; i <= lenb; ++i){
        to[i] = occ[b[i]];
    }

    int ans = lena;
    for(int i = 1; i <= lena; ++i){
        if(!vis[i]){
            --ans;
            int p = to[i]; vis[i] = true;
            while(p != i){
                vis[p] = true;
                p = to[p];
            }
        }
    }
    W(ans);
    return 0;
}