#include <stdio.h>

int main() {

    int n;
    scanf("%d",&n);

    int part[n];
    part[0] = 0;
    part[1] = 0;
    part[2] = 1;
    part[3] = 1;
    
    for(int i = 4; i <= n; i++){
        part[i] = part[i-2] + part[i-3];
    }
    
    printf("%d", part[n]);

    return 0;
}