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Copy path1166A. Silent Classroom.cpp
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1166A. Silent Classroom.cpp
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/***
Bismillahir Rahmanir Rahim
Read in the name of Allah, who created you!!!
Author : Shah Newaj Rabbi Shishir,
Department of CSE, City University, Bangladesh.
***/
#include <bits/stdc++.h>
using namespace std;
#define jeno_joyer_khuda_thake int main (void)
#define kaj_shesh return 0
#define sf scanf
#define pf printf
#define ssf sscanf
#define spf sprintf
#define fsf fscanf
#define fpf fprintf
#define fast ios_base::sync_with_stdio(0),cin.tie(0),cout.tie(0)
#define scase sf ("%d",&tc)
#define whilecase while (tc--)
#define sn sf ("%d",&n)
#define eof while (cin >> n)
#define pcase pf ("Case %d: ",pos)
#define llu unsigned long long
#define lld long long
#define U unsigned int
#define for0(i,n) for (i=0; i<n; i++)
#define for1(i,n) for (i=1; i<=n; i++)
#define forab(i,a,b) for (i=a; i<=b; i++)
#define rof0(i,n) for (i=n-1; i>=0; i--)
#define rof1(i,n) for (i=n; i>=1; i--)
#define rofab(i,a,b) for (i=b; i>=a; i--)
#define c(str) cin >> str
#define g(str) getline (cin,str)
#define vi vector <int>
#define vlld vector <lld>
#define si set <int>
#define slld set <lld>
#define ss set <string>
#define vs vector <string>
#define pii pair <int,int>
#define mii map <int,int>
#define msi map <string,int>
#define pb push_back
#define in insert
#define B begin()
#define E end()
#define F first
#define S second
#define iterate(it,x) for (it=x.B; it!=x.E; it++)
#define sort(x) sort (x.B,x.E)
#define sortR(x,a,b) sort (x.B+a,x.B+b+1)
#define rev(x) reverse (x.B,x.E)
#define revR(x,a,b) reverse (x.B+a,x.B+b+1)
#define end1 "\n"
const int MOD = 1000000007;
const int MAX = 1000005;
const double PI = acos(-1.0);
int SetBit (int n, int X) { return n | (1 << X); }
int ClearBit (int n, int X) { return n & ~(1 << X); }
int ToggleBit (int n, int X) { return n ^ (1 << X); }
bool CheckBit (int n, int X) { return (bool)(n & (1 << X)); }
jeno_joyer_khuda_thake
{
/*
freopen ("input.txt","r",stdin);
freopen ("output.txt","w",stdout);
*/
int n,i,a,b,p,ans;
string str;
while (cin >> n)
{
map <char,int> mp;
map <char,int> :: iterator it;
ans = 0;
while (n--)
{
cin >> str;
++mp[str[0]];
}
for (it=mp.B; it!=mp.E; it++)
{
p = it->S;
if (p & 1)
{
a = p/2;
b = p-a;
ans += (a*(a-1)+b*(b-1))/2;
}
else
{
a = p/2;
ans += a*(a-1);
}
}
pf ("%d\n",ans);
mp.clear();
}
kaj_shesh;
}