count the pat

counting the pat

int main()

{
int p=0, pa=0, pat = 0;
char s[100000] = { 0 };
scanf("%s", s);
int i = 0;
while (s[i]!=0)
{
switch (s[i])
{
case 'P':
p++;
break;
case 'A':
pa += p;
pa %= 1000000007;
break;
case 'T':
pat += pa;
pat %= 1000000007;
break;
}
i++;
}
printf("%d\n", pat);
return 0;
}