LIMA, PERU - Patricia Calvino has marked every day spent in a Peruvian prison on drug charges since 2013 with a cross through a calendar, a sobering reminder of how long she has spent away from her daughter in Spain.

Three years and seven months later, Calvino will join 30 other Spanish prisoners on Thursday on a flight back home - the largest repatriation of Spaniards serving prison sentences abroad in the European nation's history.

Peru is the world's second-largest cocaine producer, and much of the narcotics arriving in Europe passes through Spain, where traffickers prowl for recruits like Calvino in nightclubs, offering a hefty sum to travel to Lima and bring back cocaine.

There are currently more than 200 Spaniards in Peruvian prisons on drug charges, more inmates than from any other foreign country.

The Associated Press visited Spanish inmates at a prison near the Andean country's capital on Wednesday. The agreement under which they will leave on Thursday was brokered between the two countries to allow the inmates to serve the rest of their sentences in Spain.

"I do not sleep," said Calvino, 26, cooling herself with a black fan in a passageway at the Piedras Gordas II prison, on a hill near Lima's desert coast. "I cannot imagine the hour when I can arrive and embrace my family."

Calvino, who is from Mieres, a town of 45,000 in northern Spain, offered no excuses to justify her crime and said it had taught her an important lesson: the value of the smallest liberties, even, sipping a glass of water.

Like many "drug mules," Calvino said she was recruited in a club and offered $10,725 to fly to Peru and return with luggage containing cocaine. At the time, she was a new mother in need of money. Officials at Lima's airport caught her with 3.6 kilograms of cocaine as she was about to board a flight to Madrid.

She spent her first night detained sitting on a chair cuffed by the hands and feet at the airport's anti-narcotics division. She later slept on a mattress she remembers as being filthy and full of fleas.

One of the most painful parts of experience was being separated from her daughter, who was born just a few months before the ill-fated trip.

Inmates say the distance from their native Spain means that many don't receive visitors and this increases their loneliness.

Angel Lopez Berlanga, a 45-year-old native of Madrid serving a 12-year sentence for drug trafficking, said that since he arrived in the Peruvian prison in 2008 more than a dozen Spanish inmates have died from various diseases, including hepatitis. "But I believe also from sadness because many never received a visitor because their families are far away," said Berlanga, who will finish his sentence in Spain.

Aside from the 30 prisoners still serving sentences, 19 former inmates who have been living as indigents in Lima with no means of paying for their return trip to Spain will also be on Thursday's charter flight, Spanish Minister of Foreign Affairs and Cooperation Alfonso Dastis has said.

More than 1,700 Spaniards were jailed abroad in 2014, and the largest contingent was in Peru, according to Spanish government figures. In Peru, the foreign inmates are housed in a special pavilion.

"Many talk about doing it out of economic necessity, of being short of money," Calvino said of those caught carrying drugs. "But really, it's from a lack of values."