Why Mexico's young people are 'tired of living in fear'
The number 43 means something totally new in Mexico.
It's been painted on the banners and faces of thousands of protesters who are angry at the way the government's dealt with the disappearance of 43 students.
The group were on their way to a political rally in the city of Iguala seven weeks ago, when police attacked them.
Campaigners claim the government has done nothing to help find them.
The story so far
The 43 were reportedly handed over to a drugs gang.
Thirty-eight burnt corpses have been dug up near to the place they vanished. However, forensic tests have so far been inconclusive and have given the families no answers.
Even though more than 100,000 have been killed or "disappeared" in Mexico over the last decade, it's this case which is causing international outcry.
Newsbeat has spoken to a Mexican student living in London about life back home and how she feels about the missing 43.
"Hi, I'm Pau and I'm 26. I've lived in Mexico City all my life.
"We don't feel safe. There is the risk of kidnap every day, you can't take public transport because someone might attack you with a gun.
"The police, the government and the drugs gangs are all together like one team and we feel that nobody is protecting us," she says.
Pau was shocked when she heard about the missing students and hopes their deaths will start a revolution.
"It means that if you want to protest to ask for your rights, for freedom, you are going to be disappeared or kidnapped.
"It's too much. We are tired of living in fear. The government tries to pretend that everything is ok, but no, not really. Everybody's tired."
Pau's student visa will run out soon and she will have to go back to Mexico.
She is worried about what happens when she does.
"When I go back I will live in a much more closed way. I will be on the side of the protestors but I will be frightened," she explained.
Demonstrators have also called for a nationwide strike. Protests have also taken place in other parts of Mexico and abroad.
"We have one way to claim our rights. If we are afraid and don't say anything this will continue," says Pau.
"We have the courage to do it no matter what," she added.
The Mexican government has accused some of the protesters of trying to "destabilise" the state and says they will do all they can to find the students and bring justice for their families.