#include <stdio.h>

int main(void){
    int s, tree = 0, t = 0, r = 0, e = 0;

    while(1){
        s = getchar();
        if(t>=1 && r>=1 && e>=2){
            tree++;
            t--;
            r--;
            e-=2;
        }
        if(s=='t'){
            t++;
        }else if(s=='r'){
            r++;
        }else if(s=='e'){
            e++;
        }else if(s=='\n' || s==EOF){
            printf("%d\n", tree);
            return 0;
        }
    }
}