class py_solution:  
    def roman_to_int(self, s):  
        rom_val = {'I': 1, 'V': 5, 'X': 10, 'L': 50, 'C': 100, 'D': 500, 'M': 1000}  
        int_val = 0  
        for i in range(len(s)):  
            if i > 0 and rom_val[s[i]] > rom_val[s[i - 1]]:  
                int_val += rom_val[s[i]] - 2 * rom_val[s[i - 1]]  
            else:  
                int_val += rom_val[s[i]]  
        return int_val  
  
print(py_solution().roman_to_int('MMMCMLXXXVI'))  
print(py_solution().roman_to_int('MMMM'))  
print(py_solution().roman_to_int('C'))  