Untitled

#include <bits/stdc++.h> 


int firstCircularTour(vector<int>& petrol, vector<int>& distance, int N)
{
    int balance=0;
    int deficit=0;
    int start=0;
    for(int i=0;i<N;i++){
		balance+=petrol[i]-distance[i];
        if(balance<0){
            start=i+1;        //no need to check from start to i as if i fail from i i will fail from 0 as from 0 
            deficit+=balance; // i get some extra petrol before i reach i
			balance=0;
        }   
    }

//	return balance+deficit;
    if(balance+deficit>=0) return start;
    else return -1;
}