Below is an instruction that describes a task. Write a response that appropriately completes the request.

### Instruction:
Who was the lead envoy of the congratulation mission in 1718 with the Ryūkyūan King shō kei?

### Inputs:
table_name: table, columns: ['Year', 'Mission type', 'Shogun', 'Ryūkyūan King', 'Lead Envoy', 'Number in entourage']

### Response:
SELECT Lead Envoy FROM table WHERE Ryūkyūan King = shō kei AND Mission type = congratulation AND Year = 1718