class Solution {

public int canCompleteCircuit(int[] gas, int[] cost) {

int sum = 0;

int n = gas.length;

int pSum = 0;

int cand = -1;

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

int t = gas[i] - cost[i];

sum += t;

pSum += t;

if(pSum < 0) {

cand = -1;

pSum = 0;

}else{

if(cand == -1) cand = i;

}

}

if (sum < 0) return -1;

return cand;

}

}