#include <stdio.h>

int main()
{
    int n, r;
    scanf("%d", &n);
    
    r = 0;
    while(1){
        int b = n % 10;
        if(b == 3){
            r++;
            n /= 10;
        } else if(n == 1){
            break;
        } else {
            r = -1;
            break;
        }
    }
    printf("%d\n", r);
}