{"pre_text": ["table of contents ( 4 ) the increase in cash flows was primarily due to the timing of inventory purchases and longer payment terms with certain vendors .", "in order to manage our working capital and operating cash needs , we monitor our cash conversion cycle , defined as days of sales outstanding in accounts receivable plus days of supply in inventory minus days of purchases outstanding in accounts payable , based on a rolling three-month average .", "components of our cash conversion cycle are as follows: ."], "post_text": ["( 1 ) represents the rolling three-month average of the balance of accounts receivable , net at the end of the period , divided by average daily net sales for the same three-month period .", "also incorporates components of other miscellaneous receivables .", "( 2 ) represents the rolling three-month average of the balance of merchandise inventory at the end of the period divided by average daily cost of sales for the same three-month period .", "( 3 ) represents the rolling three-month average of the combined balance of accounts payable-trade , excluding cash overdrafts , and accounts payable-inventory financing at the end of the period divided by average daily cost of sales for the same three-month period .", "the cash conversion cycle was 19 days at december 31 , 2017 and 2016 .", "the increase in dso was primarily driven by higher net sales and related accounts receivable for third-party services such as saas , software assurance and warranties .", "these services have an unfavorable impact on dso as the receivable is recognized on the consolidated balance sheet on a gross basis while the corresponding sales amount in the consolidated statement of operations is recorded on a net basis .", "this also results in a favorable impact on dpo as the payable is recognized on the consolidated balance sheet without a corresponding cost of sales in the statement of operations because the cost paid to the vendor or third-party service provider is recorded as a reduction to net sales .", "in addition , dpo also increased due to the mix of payables with certain vendors that have longer payment terms .", "the cash conversion cycle was 19 and 21 days at december 31 , 2016 and 2015 , respectively .", "the increase in dso was primarily driven by higher net sales and related accounts receivable for third-party services such as saas , software assurance and warranties .", "these services have an unfavorable impact on dso as the receivable is recognized on the balance sheet on a gross basis while the corresponding sales amount in the statement of operations is recorded on a net basis .", "these services have a favorable impact on dpo as the payable is recognized on the balance sheet without a corresponding cost of sale in the statement of operations because the cost paid to the vendor or third-party service provider is recorded as a reduction to net sales .", "in addition to the impact of these services on dpo , dpo also increased due to the mix of payables with certain vendors that have longer payment terms .", "investing activities net cash used in investing activities increased $ 15 million in 2017 compared to 2016 .", "capital expenditures increased $ 17 million to $ 81 million from $ 64 million for 2017 and 2016 , respectively , primarily related to improvements to our information technology systems .", "net cash used in investing activities decreased $ 289 million in 2016 compared to 2015 .", "the decrease in cash used was primarily due to the completion of the acquisition of cdw uk in 2015 .", "additionally , capital expenditures decreased $ 26 million to $ 64 million from $ 90 million for 2016 and 2015 , respectively , primarily due to spending for our new office location in 2015 .", "financing activities net cash used in financing activities increased $ 514 million in 2017 compared to 2016 .", "the increase was primarily driven by changes in accounts payable-inventory financing , which resulted in an increase in cash used for financing activities of $ 228 million and by share repurchases during 2017 , which resulted in an increase in cash used for financing activities of $ 167 million .", "for more information on our share repurchase program , see part ii , item 5 , 201cmarket for registrant 2019s common equity , related stockholder matters and issuer purchases of equity securities . 201d the increase in cash used for accounts payable-inventory financing was primarily driven by the termination of one of our inventory financing agreements in the fourth quarter of 2016 , with amounts ."], "table": [["( in days )", "december 31 , 2017", "december 31 , 2016", "december 31 , 2015"], ["days of sales outstanding ( dso ) ( 1 )", "52", "51", "48"], ["days of supply in inventory ( dio ) ( 2 )", "12", "12", "13"], ["days of purchases outstanding ( dpo ) ( 3 )", "-45 ( 45 )", "-44 ( 44 )", "-40 ( 40 )"], ["cash conversion cycle", "19", "19", "21"]], "table_ori": [["", "December 31,"], ["(in days)", "2017", "2016", "2015"], ["Days of sales outstanding (DSO)<sup>(1)</sup>", "52", "51", "48"], ["Days of supply in inventory (DIO)<sup>(2)</sup>", "12", "12", "13"], ["Days of purchases outstanding (DPO)<sup>(3)</sup>", "(45)", "(44)", "(40)"], ["Cash conversion cycle", "19", "19", "21"]]}

Question: in data what was the average cash conversion cycle for the three year period?
Evidence:
table_4: ( in days ) the cash conversion cycle of december 31 , 2017 is 19 ; the cash conversion cycle of december 31 , 2016 is 19 ; the cash conversion cycle of december 31 , 2015 is 21 ;
Program: table_average(cash conversion cycle, none)
Answer:
str_answer: 19.7
exe_answer: 19.66667