A satellite was sent to Mars to take samples of it's soil and analyse the contents. It was working on solar cells. For the soil analyser to work, all it's solar cells (10 numbers) should be charged. On a single day 5 solar cells get charged. But during the night 4  of the cells get discharged. So, can you find from which day the soil analyser will start to work?
Note: All the solar cells were in discharged condition when the satellite reached Mars and it was day time when it reached.