I wonder why the output is 21?

Question

#include <iostream>
using namespace std;
int main(int argc, char *argv[])
{
int a=1;
for (int i=0; i<20; i++)
{
a++;
}
cout << a;
return 0;
}

Answer 1

1st interaction
i=0 0<20 so a=2
Then i=1 a=3
i=2 a=4
i=3 a=5
i=4 a=6
i=5 a=7
i=6 a=8
~~~~~
i=19 a=21
Am I right?

Answer 2

Thank you Jamie🌷