#include<bits/stdc++.h>
using namespace std;
int main(){
    int a,b,c;cin>>a>>b>>c;
    vector<bool> dp(a*b+5,false);
    queue<int> q;
    q.push(0);
    while(!q.empty()){
        auto t=q.front();q.pop();
        if(t+a<dp.size()&&!dp[t+a]){
            dp[t+a]=true;q.push(t+a);
        }
        if(t+b<dp.size()&&!dp[t+b]){
            dp[t+b]=true;q.push(t+b);
        }
        if(t+c<dp.size()&&!dp[t+c]){
            dp[t+c]=true;q.push(t+c);
        }
    }
    int ans=0;
    for(int i=1;i<a*b+5;i++)if(!dp[i])ans++;
    cout<<ans<<endl;
}