GCD
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#include <stdio.h>
int GCD(int a, int b){
int r = 0;
while(a != 0){
r = b%a;
b = a;
a = r;
}
return b;
}
int main(){
int n;
while(scanf("%d",&n) != EOF){
int G = 0;
if(n == 0)
break;
for(int i=1; i<n; i++){
for(int j=i+1; j<=n; j++)
G += GCD(i, j);
}
printf("%d\n", G);
}
return 0;
}
Cpp
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