In this kata, you will do addition and subtraction on a given string. The return value must be also a string.
**Note:** the input will not be empty.
## Examples
```
"1plus2plus3plus4"  --> "10"
"1plus2plus3minus4" -->  "2"
```
def calculate(s):
    # your code here
    t=s.replace("plus","+")
    y=t.replace("minus","-")
    #print(y)
    return str(eval(y))

def calculate(s):
    # your code here
    t=s.replace("plus","+")
    y=t.replace("minus","-")
    #print(y)
    return str(eval(y))
