C :

#include<stdio.h>
#include<string.h>
char a[2000000];
int main()
{
    int len,i;
    long long rec,ans;
    while(scanf("%s",a)!=EOF)
    {
        rec=0;ans=0;
        len=strlen(a);
        for(i=0;i<len;i++)
        {
            if(a[i]=='h'&&a[i+1]=='e'&&a[i+2]=='a'&&a[i+3]=='v'&&a[i+4]=='y')
            {
                i+=4;
                rec++;
            }
            else if(a[i]=='m'&&a[i+1]=='e'&&a[i+2]=='t'&&a[i+3]=='a'&&a[i+4]=='l')
            {
                i+=4;
                ans=ans+rec;
            }
        }
        printf("%lld\n",ans);
    }
    return 0;
}

C++ :

#include<iostream>
#include<string.h>
using namespace std;
string s;
int main()
{
    while(cin>>s)
    {
        int length=s.length();
        long long a=0,b=0;
        for(int i=0;i<length;i++)
        {
            if(s[i]=='h'&&s[i+1]=='e'&&s[i+2]=='a'&&s[i+3]=='v'&&s[i+4]=='y')
            {
                i+=4;
                a++;
            }
            if(s[i]=='m'&&s[i+1]=='e'&&s[i+2]=='t'&&s[i+3]=='a'&&s[i+4]=='l')
            {
                i+=4;
                b+=a;
            }
        }
        cout<<b<<endl;
    }
    return 0;
}