C :

#include <stdio.h>
#include <string.h>
int main()
{
    char str[200];
    while(gets(str))
    {
        char ch1[10] = "think";
        char ch2[10] = "different";
        int len = strlen(str);
        int f = 0;
        for(int i = 0; i < len; i++)
        {
            if(str[i]==' '&& i>4 && i+9<len)
            {
                int k = 0;
                for(int j = i-5; j < i; j++)
                    {
                        if(str[j]==ch1[k]||str[j]+32==ch1[k])
                        k++;
                    }
                if(k==5)
                {
                    k = 0;
                    for(int j = i+1; j <= i+9; j++)
                    {
                        if(str[j]==ch2[k]||str[j]+32==ch2[k])
                            k++;
                    }
                }
                if(k==9) f++;
            }
        }
        printf("%d\n", f);
    }
}

C++ :

#include <iostream>
#include <string>
using namespace std;

int main() {
	string s, sub, t = "think different";
	int i, ans;
	while (getline(cin, s)) {
		for (i = 0; i < s.length(); i++)
			if (s[i] >= 'A' && s[i] <= 'Z')
				s[i] += 32;
		for (ans = i = 0; i < s.length(); i++) {
			if (i + 14 < s.length()) {
				sub = s.substr(i, 15);
				if (sub == t)
					ans++;
			}
		}
		cout << ans << endl;
	}
	return 0;
}