#include <bits/stdc++.h>
#define pb push_back
#define ff first
#define ss second
#define M 1000001
typedef long long ll;
const int p=53;
const long long MOD=1000000007;
using namespace std;
ll a[M],b[M],c[M],d[M];
ll pow2[M];
ll power(ll a,ll b){
ll res=1;
while(b>0){
if(b&1){
res=res*a;
if(res>=MOD) res%=MOD;
}
b>>=1;
a=a*a;
if(a>=MOD) a%=MOD;
}
return res;
}
ll turn(ll k){
return (k+10*MOD)%MOD;
}
ll suma,sumb,sumgiven;
int main(){
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
int n;
cin >> n;
pow2[0]=1;
for(int i=1;i<=n;i++){
pow2[i]=pow2[i-1]*2;
if(pow2[i]>=MOD) pow2[i]%=MOD;
}
for(int i=0;i<n;i++){
cin >> a[i] >> b[i];
suma+=a[i];
sumb+=b[i];
c[i]=a[i]-b[i];
}
long long res=0;
for(int i=1;i<n;i++){
res+=((turn(c[i])*pow2[i-1])%MOD);
if(res>=MOD) res%=MOD;
}
bool flag=0;
res+=((c[0]*pow2[n-1])%MOD);
if(res>=MOD) res%=MOD;
res=res*power(pow2[n]-1,MOD-2);
if(res>=MOD) res%=MOD;
d[0]=res;
sumgiven=d[0];
for(int i=1;i<n;i++){
ll e=c[i]+d[i-1];
if(e&1){
cout << "No";
return 0;
}
d[i]=e/2;
sumgiven+=(d[i]);
if(d[i]<0){
cout << "No";
return 0;
}
if(d[i-1]+a[i]<2*d[i]){
cout << "No";
return 0;
}
if(a[i]>=2*d[i]) f=1;
}
if(d[n-1]+a[0]<2*d[0]){
cout << "No";
return 0;
}
if(c[0]-2*d[0]+d[n-1]!=0){
cout << "No";
return 0;
}
if(sumgiven+sumb!=suma){
cout << "No";
return 0;
}
if(f==0){
cout << "No";
return 0;
}
cout << "Yes";
return 0;
}
Compilation message
remittance.cpp: In function 'int main()':
remittance.cpp:74:20: error: 'f' was not declared in this scope
74 | if(a[i]>=2*d[i]) f=1;
| ^
remittance.cpp:88:5: error: 'f' was not declared in this scope
88 | if(f==0){
| ^
remittance.cpp:51:7: warning: unused variable 'flag' [-Wunused-variable]
51 | bool flag=0;
| ^~~~
