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

### Instruction:
Who was the President of Czechoslovakia when an ambassador's tenure began in 1950?

### Inputs:
table_name: table, columns: ['Name', 'Tenure Begin', 'Tenure End', 'British monarch', 'Czechoslovak president']

### Response:
SELECT Czechoslovak president FROM table WHERE Tenure Begin = 1950