#include <stdio.h>
#define s 2
#define m 2
int main(){
int i,j;float score[s][m];
void average(float score[s][m]);
for(i=0;i<s;i++)
for(j=0;j<m;j++)
scanf("%f",&score[i][j]);
average(score);
return 0;
}
void average(float score[s][m]){
int i,j;float sum=0,aver;
for(i=0;i<s;i++)
sum=sum+score[i][0];
aver=sum/s;
printf("%f",aver);
}