Besides the Navy, Generalissimo Guards and twenty battalions of the Guangdong Army, Sun Yat-sen lacked strong support of military strength in the Guangzhou Military Government, and sometimes his order was only effective in the Generalissmo Government. Sun had thoughts of mutiny at once, hoping to overthrow the Guangxi influence, and had personally ordered the Navy to fire at the Guangxi headquarters at one time. Near the end of 1917, Lu Rongting, Tang Jiyao, Mo Rongxin and others along with Tang Shaoyi convened a conference, and they advocated recognition of Feng Guozhang's presidency and formation a united government. During 1918, Cheng Biguang aligned himself with the Guangxi clique, and was assassinated. The Extraordinary Session of Parliament was controlled by the Guangxi clique, and was restructured in May 1918 by replacing the office of generalissimo with a committee of seven executives consisting of Sun, Tang Shaoyi, Wu Tingfang, and Tang Jiyao on one side and Lu Rongting, Cen Chunxuan, and Lin Baoyi on the other. Feeling marginalized, Sun Yat-sen resigned as the generalissimo, and left Guangzhou for Shanghai. The Guangzhou Military Government was now headed by Cen Chunxuan, the chief executive. Wu Tingfang's election as Guangdong's governor was nullified by Lu Rongting. From February to August 1919, the North and South held negotiations in Shanghai but they were stalled by Duan's sabotage.  All MPs who did not attend the southern "extraordinary" session were disqualified and replaced.  Parliament was adjourned by its Speaker Lin Sen on January 24, 1920 when a faction of MPs boycotted the assembly, depriving it of a quorum.  Cen also suspended the salaries of the MPs.  With the southern government effectively under the influence of the Old Guangxi Clique, the first constitutional protection movement was over.. How many months did the negotiations between the North and South last in 1919?