On 1 April 1911, Porfirio Díaz claimed that he had heard the voice of the people of Mexico, replaced his cabinet, and agreed to restitution of the lands of the dispossessed. Madero did not believe this statement and instead demanded the resignation of President Díaz and Vice-President Ramón Corral. Madero then attended a meeting with the other revolutionary leaders - they agreed to a fourteen-point plan which called for pay for revolutionary soldiers; the release of political prisoners; and the right of the revolutionaries to name several members of cabinet. Madero was moderate, however. He believed that the revolutionaries should proceed cautiously so as to minimize bloodshed and should strike a deal with Díaz if possible. In May, Madero wanted a ceasefire, but his fellow revolutionaries Pascual Orozco and Francisco Villa disagreed and went ahead with an attack on Ciudad Juárez. The revolutionaries won this battle decisively and on 21 May 1911, the Treaty of Ciudad Juárez was signed. Under the terms of the Treaty of Ciudad Juárez, Díaz and Corral agreed to resign by the end of May 1911, with Díaz's Minister of Foreign Affairs, Francisco León de la Barra, taking over as interim president solely for the purpose of calling general elections. This first phase of the Mexican Revolution thus ended with Díaz leaving for exile in Europe at the end of May 1911. On 7 June 1911, Madero entered Mexico City in triumph where he was greeted with huge crowds shouting "¡Viva Madero!"
Question: Corral agreed to resign how many months before Madero entered Mexico City in triumph?
Answer: 1