Do you have the brainwave???

I was heading on my car from Mumbai to Patna. While traveling from Mumbai to Patna, I have lost my way. But I kept on driving the car and I am now in a four-way junction where there is a signboard which has fallen off its post. It has been marked as Patna, Goa, Mumbai and Bangalore. But i believed that the signboard will help me to find out the way to Patna. Luckily I had a brainwave which helped me out to find the way for Patna. What was my idea?

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