import java.io.IOException;
import java.io.InputStream;
import java.util.Scanner;
public class Main {
    static int len;
    static int read;

    static final char[] chars="CPCT".toCharArray();
    static final char[] CPC="CPC".toCharArray();
    static int last=0;
    public static void main(String[] args) {
        FastScanner scanner=new FastScanner();

        len=scanner.readInt();
        int o=0;
        while (read<len){
            skipTillCPCT(last,scanner);
            if(ableToBeF(scanner)) o++;
        }
        System.out.println(o);
    }
    private static boolean ableToBeF(FastScanner scanner){
        int c=read(scanner);
        if(c=='F') return true;
        if(c!='C') return false;
        if((last=read(scanner))!='P') return false;
        if((last=read(scanner))!='C') return false;
        last=0;
        return true;
    }
    private static void skipTillCPCT(int last,FastScanner scanner){
        int c;
        int index=0;
        if(last=='C') index++;
        last=0;
        while (index!=4&&(c=read(scanner))!=-1){
            if(c!=chars[index]){
                index=0;
                continue;
            }
            index++;
        }
    }
    private static int read(FastScanner scanner){
        if(len<=read) return -1;
        read++;
        return scanner.readByte();
    }
    private static class FastScanner {
        private final InputStream in = System.in;
        private final byte[] buffer = new byte[1024];
        private int ptr = 0;
        private int buflen = 0;
        private boolean hasNextByte() {
            if (ptr < buflen) {
                return true;
            }else{
                ptr = 0;
                try {
                    buflen = in.read(buffer);
                } catch (IOException e) {
                    e.printStackTrace();
                }
                return buflen > 0;
            }
        }
        private int readByte() {
            if (hasNextByte()){
            return buffer[ptr++];
        } else return -1;}
        private static boolean isPrintableChar(int c) { return 33 <= c && c <= 126;}

        public int readInt(){
            int b = readByte();
            int n=0;
            while(true){
                if ('0' <= b && b <= '9') {
                    n *= 10;
                    n += b - '0';
                }else if(b == -1 || !isPrintableChar(b)){
                    return n;
                }else{
                    throw new NumberFormatException();
                }
                b = readByte();
            }
        }
    }
}