#include <bits/stdc++.h>
using namespace std;
int main(){
    int n;
    float h;
    cin>>n;
    h=(n-2)*180.0;
    printf("%./n",h);
	
	    
 
}
/**************************************************************
	Problem: 1005
	User: wngjinming
	Language: C++
	Result: Wrong Answer
****************************************************************/