/*
#include <stdio.h>
int main()
{
char x[201];
int n, i, b;
scanf("%d",&n);
b=(3-(n%3))%3;
for (i=1; i<=n; i++)
{
scanf("%s", x[i]);
}
}
#include <stdio.h>
char x[201],k[20100000];
int main()
{
int n, i, b=0 ,top=1;
scanf("%d",&n);
scanf("%s", x);
for (i=n-1;i>=0;i--)
{
if (b==3)
{
b=0;
k[top]=',';
top++;
}
k[top]=x[i];
b++;
top++;
}
for(i=top-1;i>=1;i--)
{
printf("%c",k[i]);
}
0;
}
*/