Pat 1050 string subtraction (20 points) string find

#include <iostream>
using namespace std;
int main() {
    
    string s1,s2;
    getline(cin,s1);
    getline(cin,s2);
    for(int i=0;i<s1.length();i++){
    
        if(s2.find(s1[i])==string::npos)
            printf("%c",s1[i]);
    }
    return 0;
}