#include <iostream>
#include <cstdio>

#define LL long long 
#define rg register

using namespace std;

template<class T>
inline void read(T &x)
{
    x=0;
    bool f=0;
    char c=getchar();
    for(;!isdigit(c);c=getchar())
        f^=c=='-';
    for(;isdigit(c);c=getchar())
        x=x*10+(c^48);
    x=f?-x:x;
}

int precision,recall;
double ans;

int main()
{
    read(precision),read(recall);
    ans=2*precision*recall/(precision+recall);
    printf("F1 = %f",ans);
}

include

using namespace std; int main(void){ double F1; int precision,recall; cin>>precision>>recall; F1= 2*precision*recall/(precision+recall); cout<

#include<stdio.h>
int main() {
    scanf("%d %d", &precision, &recall);
    printf("F1=%d", 2 * precision * recall / (precision + recall));
    return 0;
}

void main(){long double F1;int precison;int recall;printf("F1=%d",2*precison*recall/(precision+recall))}

include

using namespace std int main() { long double F1; int precision; int recall; F1=2*precision*recall/(precision+recall); count<