#include<iostream>
#include<string>
using namespace std;
int SimpleIndex(const string &Target,const string &Old,int pos){
    int i=pos,j=0;
    while(i<Old.length()&&j<Target.length()){
        if(Old[i]==Target[j]){
            i++;
            j++;
        }else{
            i=i-j+1;
            j=0;
        }
    }
    if(j>=Target.length()){
        return i-j;
    }else{
        return -1;
    }
} 
int main(){
    string t="abc";
    string o="abdadc";
    int answer=SimpleIndex(t,o,0);
    printf("%d",answer);
    return 0;
}