Basic Calculator

s is an arithmetic expression with non-negative whole numbers, the operators +, -, *, / and optional spaces. There are no brackets. Multiplication and division come before addition and subtraction; division of whole numbers truncates toward zero. Return the value.

For "3+2*2" the answer is 7; for " 3/2 " it is 1.

Examples

Example 1

Input:

calculate('3+2*2')

Output:

7

Example 2

Input:

calculate(' 3/2 ')

Output:

1

Constraints

• 1 <= len(s) <= 100000
• The expression is valid, never divides by zero, and every intermediate value fits in 64 bits.