def getTour(petrol,distance,n):
s,start,diff=0,0,0
for i in range(n):
s=s+petrol[i]-distance[i]
if(s<0):
start=i+1
diff+=s
s=0
if s+diff>0:
return start
else:
return -1
if __name__=='__main__':
petrol=[4,6,7,4]
distance=[6,5,3,5]
value=getTour(petrol,distance,4)
print(value)