#include<iostream>

#include<string>

using namespace std;

int main(){

int n;

while(cin>>n){

string s;

for(int i=0;i<n;i++){

char c;

cin>>c;

s+=c;

}

char c;

cin>>c;

size_t f=s.find(c);

if(f!=string::npos){

cout<<f<<endl;

}else{

cout<<"No"<<endl;

}

}

return 0;

}