#include<stdio.h>
int main()
{
    int a,b,c,i;
    while( scanf( "%d%d%d",&a,&b,&c ) != EOF )
    {
        int sum = 0;
        while( a > 0 && b > 0 && c > 0 )
        {
            sum += ( a + b + c ) * 2 - 6;
            a--;
            b--;
            c--;
        }
        if( a == b && a == c )
        sum++;
        printf( "%d\n",sum );
    }
    return 0;
}